Patent Application
20150096488
N/A
The present invention relates to the field of nitride semiconductor crystal substrates that can be used in the fabrication of larger nitride semiconductor crystal or electronic and or piezoelectric devices.
Volumetric growth in vapor phase crystal systems typically occurs by two methods. First, by the homogeneous nucleation of two-dimensional/three-dimensional nuclei on the growth surface; the so called island growth mode; and second by the surface diffusion of adatoms and subsequent attachment of adatoms into surface steps by so called step flow.
The volumetric growth of crystals is a function of both thermodynamics and kinetics, and can be controlled by altering growth conditions; growth temperature, temperature gradients, and chemical potentials.
C-plane platelet growth has been easily achieved in the SiC crystal system. See U.S. Pat. No. 2,854,364 to J. A. Lely, entitled Sublimation process for manufacturing silicon carbide crystals, issued 1958; W. F. Knippenberg, Growth Phenomena in Silicon Carbide, Philips Research Reports 18 (1963) 257; and A. A. Lebedeva et. al., Growth and investigation of the big area Lely-grown substrates Materials Science and Engineering: B46 (1997) 291. Each of these references reports on the ability to produce platelets with large c-plane surface areas. Yet no reports of other crystallographic platelets such as m or a plane have ever been reported for SiC growth. In fact it is assumed that the natural growth habits of hexagonal SiC only give rise to c-plane platelets. Thus inhibiting formation of other crystallographic-plane orientated platelets. The ability to produce C-plane SiC platelets repeatability set the foundation for the growth of the SiC electronics market. It has been found to be difficult to grow spontaneous nucleation of AlN single crystals that have the large facet parallel to the “c-plane” such as with SiC.
The present disclosure generally relates to a novel systems and methods to control the growth of crystals and platelets. In particular, the present disclosure generally relates to systems and methods for growing group III-V nitride crystals and platelets, such as an aluminum nitride crystal, having a large c-plane or m-plane facet or lattice plane. The systems and methods include manipulating the volumetric growth of aluminum nitride in such a way that the c or m-plane is preferentially volumetrically expanded.
A chemical driving agent can be used with or without temperature gradients to control the preferential growth of AlN. Chemical driving agent species introduced during the growth changes the volumetric growth rate of the crystal producing large repeatable c-plane platelets at temperatures between 2000° to 2450° C. and m-plane crystals at temperatures between 2000 to 2450° C. not previously found.
The modification of aluminum nitride growth is not limited to the sublimation regime/method, nor is this process limited to AlN but is useful in the growth of ternary and more complex III-V compounds. The addition of additives, such as carbon, gallium, Indium, boron and carbon, gallium, Indium, boron bearing gases, into high temperature vapor phase epitaxy leads to preferential morphology control of the produced crystals also. Sulfur, Bismuth, and high volatility gases of Carbon, Indium, Gallium, Sulfur, Thallium, Magnesium, and Boron are useful in the lower temperature range (below 2200° C.) of these processes such as HVPE or High Temperature CVD growth.
In particular, the present disclosure relates to a method of preferably volumetrically enlarging a group III-V nitride crystal. The method includes providing a crystal growth structure and providing a crystal growth constituent, where the crystal growth constituent grows the group III-V nitride crystal on the crystal growth structure. The method also includes providing a chemical driving agent, where the chemical driving agent enhances or limits crystal growth on a particular plane of the group III-V nitride crystal.
In various aspects, the crystal growth structure is a substrate, a seed, or a previously grown-crystal. The crystal grown in accordance with the methods disclosed herein be substantially a single crystal or a platelet and may include nitrogen and at least one species of Al, Ga, and In. Moreover, one possible crystal that may be grown has a formula of AlxInyGa(1−x−y)N, where 0≧x≦1, 0≧y≦1, x+y+(1−x−y)≠1.
In one aspect, the chemical driving agent enhances growth of the previously grown-crystal from a first diameter to a second diameter without a corresponding growth in thickness. In another aspect, the chemical driving agent enhances growth of the previously grown-crystal from a first diameter to a second diameter without inducing thermal stress into the previously grown-crystal.
In one embodiment a method of preferably volumetrically enlarging a group III-V nitride crystal includes providing a crystal growth structure and providing a crystal growth constituent, where the crystal growth constituent grows the group III-V nitride crystal on the crystal growth structure. The method includes providing a chemical driving agent, where the chemical driving agent enhances or limits the mobility of a crystal growth constituent adatom at a growth surface of the group III-V nitride crystal. In one aspect, the crystal growth structure is disposed within in a reactor system and the chemical driving agent alters the surface growth kinetics of the reactor system.
In another embodiment, a method for growing and preferably volumetrically enlarging a group III-V nitride crystal includes providing a powder to an annular-shaped cavity of a crucible. The annular shaped cavity is defined by an interior surface of the crucible and a packing tube removably disposed in the crucible. The powder includes a distribution of particle sizes of at least one constituent species of the group III-V nitride crystal.
The method also includes compressing the powder to form a charge body, removing the packing tube to form a charge body cavity, where the charge body includes an exterior surface and an interior surface defining the charge body cavity. The crucible is heated to sinter the charge body. Heating the crucible further induces a thermal driving force across the charge body. The method also includes providing a chemical driving agent and soaking the crucible and the charge body at a temperature sufficient to diffuse the at least one constituent species of the group III-V nitride crystal from the exterior surface to the interior surface of the charge body. The at least one constituent species of the group III-V nitride crystal freely-nucleates in the interior surface to grow the group III-V nitride crystal in the interior cavity. The chemical driving agent enhances or limits crystal growth of the group III-V nitride crystal on a particular plane of the group III-V nitride crystal.
In another embodiment, a system for growing and preferably volumetrically enlarging a group III-V nitride crystal includes a reactor, a crucible, a chemical driving agent source, and a sintered porous body disposed with in the crucible. The sintered porous body includes an exterior surface, an interior surface defining an interior cavity and at least one constituent species of the group III-V nitride crystal.
The reactor heats the crucible to form a thermal driving force across the sintered porous body and the thermal driving force diffuses the at least one constituent species of the group III-V nitride crystal from the exterior surface to the interior surface. The at least one constituent species of the group III-V nitride crystal freely-nucleates in the interior surface to grow the group III-V nitride crystal in the interior cavity. The chemical driving agent enhances or limits crystal growth of the group III-V nitride crystal on a particular plane of the group III-V nitride crystal.
Group III-Nitride crystals of AlN, GaN, and SiC are most stable in the wurtzite crystal structure shown in
It was found that the production of the c-plane aluminum nitride platelets like those found in SiC were impossible. As reported in Natural Growth Habit of Bulk AlN Crystals, B. M. Epelbaum, Journal of Crystal Growth 265 (2004) 577, the attempts to form SiC like platelets resulted in thick asymmetrical platelets that showed many un-preferred crystal facets. During the investigation of AlN, crystal platelet thickness varied from 1 to 3 mm, but habit facets that governed the asymmetric appearance were “omnipresent”. In Development of natural habit of large free-nucleated AlN single crystals, B. M. Epelbaum et. al., physica status solidi (b) 244, No. 6, 1780-1783 (2007), it was reported, “The platelet crystals exhibit characteristic asymmetric habit with largest flat being a pseudo-facet build by alternating (1010) facets. Pronounced true facets are Al-terminated (0001) and adjacent (1012) facets, with one of them growing much larger than others. The analysis of formation history of freestanding AlN crystals made it possible to explain their habit, very unusual for wurtzite-type structure. Growth of freestanding AlN starts from a long needle formed along the (11-20) direction at lower temperature of 1900-2000° C. and continues by needle expansion and thickening along mainly (0001) direction, leading to asymmetric platelet. In such geometry only one extended (1012) facet can be developed.” It further stated, “The growth model presented here provides an answer to the curious habit of freestanding AlN based on the analysis of its growth history. The model explains specific zonar structure of freestanding AlN as well.” The perceived problems with producing freely nucleated c-plane AlN platelets in comparison to SiC platelets are also noted in Similarities and differences in sublimation growth of SiC and AlN, B. M. Epelbaum et. al., Journal of Crystal Growth 305 (2007) 317.
Very small, unintentional, freely nucleated multi m-plane/a-plane AlN crystals have been observed as a byproduct of other AlN production methods. Unfortunately morphological control to produce one dominant platelet surface and reproducibility of these platelets has proved difficult if not impossible. It has also been reported that some “spontaneously nucleated crystals exhibited an incomplete pyramid-like structure with (10-10) and (1100) as their prominent faces,” in Sublimation growth of AlN bulk crystals by seeded and spontaneous nucleation methods, K. Balakrishnan et. al., Materials Research Society (MRS) Proceedings, volume 83, 2004.
The ability to control and manipulate the growth habits of III-Nitride crystal systems, including but not limited to the crystallographic-planes and the volumetric growth, especially that of AlN and SiC, is crucial in the commercial production of these crystal systems. The m-plane surface is used in non-polar laser diode and other optical devices where the c-plane is preferred for polarization enhanced electrical devices and power electronics.
It has been now shown that spontaneously nucleated AlN crystals follow a sequence of natural volumetric growth as shown in
As disclosed in, the co-pending parent application the c-plane of the AlN system will align itself along the isotherms of the growth environment it is in. Or, in other words, the c-plane will align itself perpendicular to the largest temperature gradient inside the growth environment. In the growth environment the direction the isotherms take can be controlled. Changing the insulation and relative position of the crucible inside the reactor achieves this control over the isotherms.
In a method to growth freely nucleated AlN crystals disclosed in the co-pending parent application, it was disclosed that after loading a charge into a crucible growing crystals therein, preventing growth in the 3-D growth regime, as shown by the 3-D crystal 202, is desired. In the 3-D growth regime, pits or holes are formed in the surface parallel to the charges surface as the crystal expanse volumetrically. This is due to nanostructures formed during nucleation and a shadowing effect where the concentrations of the Al and N species change dramatically across the shadowed surface. If the nanostructures formed during nucleation on the charge or shadowing occurs on a surface that is the polar c-plane, it can cause changes in the polarity of the crystal during growth. Thus, in the present disclosure it is desirable to set or otherwise control the nanostructures formed during nucleation on the charge wall and keep the crystal growth in a near 2D growth mode where the c-plane is the dominant facet, when producing c-plane seeds and platelets 203. In the 3-D growth regime the pits or holes formed in the c-plane surface make these crystals undesirable for c-plane substrates; however a portion of the m-plane may be used. To produce m-plane crystals 301, as shown in
It has also been disclosed in the co-pending parent application, that by holding the isotherms horizontal, using isothermal horizontal thermal gradients, inside the crucible, it forces the c-plane to expand perpendicular to the charge's surface. Conversely if m-plane crystals and/or seeds are to be produced, the c-plane is set perpendicular to the charge surface. The thermal fields are changed such that the thermal gradient from top to bottom is held isothermal and a larger gradient is introduced across or radial to the crucible.
The present disclosure further relates to systems and methods of crystal growth where temperature alone is not the desired driver for AlN morphology. In various embodiments, this is accomplished by spatially confining the height of the crucible. By way of example and not limitation, the crucible height may in a range of approximately 1 mm to 3 mm, where single crystals having dimensions as large as approximately 15 mm×25 mm by 1 mm thick, shown in
While relying on temperature alone may make producing m-plate AlN crystals difficult, temperature used to control the growth morphology has produced good c-plane platelets in temperatures ranging from 2380-2420° C., as shown in
As an alternative to temperature modifications, using a chemical driving agent has been identified as a way to obtain preferential morphology control across a wide temperature regime to control preferential volumetric growth. As used herein “preferred volumetric enlargement” refers to the controllable and desired growth of a crystal structure in one or more specific planes or directions. In various embodiments, carbon is used as a chemical driving agent for forcing the AlN morphology into the c-plane platelet regime at temperatures below its natural occurrence at approximately 2400° C. Furthermore, there is a strong correlation between the concentration of the driving agent in the system and the effects on the system. For example, increasing carbon concentrations leads to increased anisotropic growth rates normal to the m-plane and c-plane, leading to thinner platelets with a large c-plane surface.
In various embodiments, the driving agent may be the gas species of carbon (C), gallium (Ga), indium (In), sulfur(S), bismuth (Bi), Boron (B), magnesium (Mg), titanium (Ti,) silicon (Si), or combinations thereof. The driving agent agents may be used in elemental form or as compounds containing one or more elements. When adsorbed on the surface of an AlN crystal, the driving agent changes the surface energy, diffusion method and diffusion length of the Al and or N adatoms on the surface. This will increase the rate of formation of stable two-dimensional AlN nuclei on certain growth facets and thus changes the volumetric growth rate of the crystal along those facets.
For chemical driving agents, such as carbon and silicon, increasing the concentration at the surface increases the change in the volumetric growth rate. However, a large amount of carbon and silicon introduced during the growth can incorporate into the crystal system and change the optical and electrical properties of the crystal. Thus, it is desirable to use a chemical driving agent that will not readily incorporate into the aluminum nitride crystal. In various embodiments, gallium, indium, and bismuth, alone or in combination, can be used to preferentially control the morphology of aluminum nitride to produce large c-plane platelets at temperatures between approximately 1800 and 2450° C. In these embodiments, it is believed that indium and gallium affect the surface energy, diffusion method and diffusion length of the Al and or N adatoms but do not significantly incorporate, to the same extent as carbon and silicon, into the aluminum nitride crystal lattice at temperatures above 1800° C. This is due, at least in part, to their higher vapor pressure and low sticking coefficients.
In various other embodiments, chemical driving agents may be used in conjunction with temperature gradients to promote and control crystal growth. For example, the addition of Boron as a chemical driving agent along with controlling the thermal profile during crystal growth can increase the rate of formation of stable two-dimensional AlN nuclei on the m-family growth planes and thus change the volumetric growth rate of the crystal along those facets. This leads to the formation of thin m-plane crystals platelets at temperatures where such growth has not been previously observed. For example, the combined use of thermal gradients and Boron as a chemical driving agent permitted the growth of thin m-plane crystals at temperatures between approximately 2000 to 2450° C.
As disclosed herein, the modification of aluminum nitride crystal growth is not limited to systems and methods that rely on sublimation. In various embodiments, the addition of additive chemical driving agents, such as carbon, gallium, Indium, boron or gases including the aforementioned elements, among others, into high temperature vapor phase epitaxy systems also leads to preferential morphology control of the produced crystals. In these embodiments, Sulfur, Bismuth, and high volatility gases of Carbon, Indium, Gallium, Sulfur, Thallium, Magnesium and Boron are useful in low temperature (below 2200° C.) growth processes, such as but not limited to HVPE or High temperature CVD growth.
The systems and methods disclosed herein are not limited to growing AlN but are useful in the growth of ternary and more complex III-V compounds. For example, HVPE may be used to grow aluminum gallium nitride (AlGaN) crystals having preferred morphology at growth temperatures as low as about 1000° C. In these examples, the chemical driving agents may include hydrocarbons, indium, sulfur, bismuth, and diborane, among others.
In various embodiments, the chemical driving agents may be any suitable form, type, phase of matter or physical composition of material. Alternately, any suitable precursor compound or compounds that will produce the desired chemical driving agent or agents in situ maybe used to promote preferential volumetric growth. For example, Gases, solids, open porous volume foams, powders, liquids, phase changing systems, or any other volatile or nonvolatile compound containing the desired chemical driver agent elements can be used, including oxides. As understood by one skilled in the art, these materials could be placed in proximity to the crystal growth \surface, intermixed within any starting material or gas stream used to produce the III-N crystal, incorporated into structural support or non-supporting structural components in a suitable reactor system. For example, chemical driving agent or precursors thereof may be incorporated into or positioned proximal to thermal insulation, support structures, crucibles, and/or retorts.
In various embodiments, the chemical driving agent may be used or otherwise activated to preferentially and volumetrically augment crystal at will. For example, the crystals exposure to the chemical driving agent may be toggled on and off or ramped up during the growth. In other examples, the concentration, volume, time of exposure, and other parameters related to the deployment of the chemical driving agent may be varied. In one particular example, a solid chemical driving agent may be used in conjunction with a gaseous driving agent, such that the application of the gaseous driving agent may be modified or even stopped to provide varied combinations for the chemical driving agents deployed. This allows for the preferential volumetric expansion in one plane until a desired size or volume expansion has been achieved. The growth direction may then be altered by promoting growth in a different plane using thermal gradients, chemical driving agents, or both. In one embodiment, this is accomplished, by reducing or eliminating one chemical driving agent thus permitting non-preferential volumetric expansion.
In other embodiments, by toggling between different agents (e.g., introducing second agent that will preferentially volumetrically expand the crystal in another plane) preferential three-dimensional growth can be obtained. For example, this may be accomplished by switching between a carbon based driving agent and a boron-based driving agent. In this example, a carbon containing gas, giving preferential volumetric expansion in the c-plane, is introduced into a system for growing crystals using HVPE. A boron containing gas, giving preferential volumetric expansion in the m-plane, may then be used. Moreover, one driving agent component may be a passive solid such as, a solid source of carbon, and the other agent may be a boron containing gas that can be actively modified, during the growth process.
In another embodiment, a chemical driving agent, such as Carbon and/or Boron, can be employed in a sublimation reactor in a two-step process to first expand out (in diameter) a AlN seed crystal on a preferred lattice plane then second grow down (in length) on that same lattice plane or another plane. In similar embodiment, at least two growth regimes may be used. One growth regime preferentially grows the crystal along one plane, while the second growth regime preferentially grows in the crystal on another plane by: 1) changing the thermal fields in the presence of a chemical driving agent; 2) changing the chemical driving agents in the presence of a static thermal profile; or 3) changing both the chemical driving agent and the thermal profile during the growth. This can be accomplished in separate processes where the crystal is heated and grown under one regime, cooled down and repositioned for growing under the second regime. Alternatively, the both regimes may be used concurrently little or no changes in the thermal fields. The growth regimes may be deployed in a discreet cyclic manner or the transitions between the two regimes can be identified by a smooth gradient change from one driving agent concentration to another or from one thermal profile to another.
In one embodiment of growing crystals using a sublimation technique, shown in
When considering the first and third factors, it has been determined that changes in the X-Y-Z temperature gradient and the X-Y concentration of the driving agent species gradient can modify the growth habits of the crystal, as shown in
In typical growth normal to the c-plane without chemical driving agents, as shown in
When used in appropriate quantities, the chemical driving agents act as a buffer thereby evening out or nullifying the temperature gradient, thus resulting in more uniform crystal growth as shown in
Typically, expansion of the AlN crystal diameter during sublimation growth is brought about by using a concave temperature profile, shown by 2204 in
For growth perpendicular to the m-plane, the addition of chemical driving agents such as carbon can be used to offset the need to control the isotherms. As shown in
Referring now to
As shown in
By way of example and not limitation, in one particular embodiment, approximately 1.5 kg of AlN powder mixed with carbon powder as to be used as the chemical driving agent that enhances volumetric expansion charge 401 is loaded inside a hollow crucible 403 having an internal diameter of approximately 6 inches about an internal packing tube 405 having a diameter of approximately 3 inches. The packing tube 405 is positioned within the crucible along a central longitudinal axis 408 of within the crucible, as shown in
The charge 401 is compressed between the interior wall 407 of the crucible 403 and the external surface 409 of the packing tube 405. The powder charge 401 is pressed, at least a sufficient amount, for the charge to retain its shape and define the cavity 402, after the internal packing tube 405 is removed. The result is a charge body 601 having internal surfaces 411 that define the internal cavity 402. In other embodiments, other combinations of the diameters for the crucible 403 and the packing tube 405 may be used to create charge bodies of any desired thickness 412.
The crucible 402 including the charge body 601 (hereinafter referred to as packed crucible 60) is placed in a reactor 70, as shown in
By way of example and not limitation, one embodiment of the reactor 70 uses induction heating. In this embodiment, the packed crucible 60 is heated by a susceptor 701 positioned within a radio frequency induction field generated by the radio frequency induction coil 703. The susceptor 701 can be composed of any suitable and susceptible material, such as tungsten (W), for example. The reactor 70 also includes thermal insulation 704 positioned at the top 705 and bottom 707 portions of the reactor interior 708 moderate the thermal fields with the reactor interior. The thermal fields with the reactor 70 are also controlled and or modified by the positioning of the susceptor 701 within the reactor and the length, coil-to-coil gaping, and positioning of the radio frequency induction coil 703.
Prior to heating the crucible body 60, the reactor 70 may be evacuated to vacuum pressures, backfilled, purged, and evacuated again. In one embodiment using a charge body 601 composed of AlN, the reactor is evacuated to a vacuum at or below 1×10−2 torr, backfilled/purged with nitrogen, and then evacuated again to a vacuum at or below 1×10−2 torr. In this embodiment, the crucible body 601 is heated under vacuum to approximately 1700° C. for approximately 2 hours. In one aspect, this initial heating is used to sinter the AlN charge body 601.
After this initial heating, the reactor 70 is backfilled with nitrogen to a pressure of approximately 980 torr, in one embodiment. The temperature of the crucible body 601 is then increased to 2100-2450° C. over a period of approximately one hour and allowed to soak at 2100-2450° C. for approximately 30 hours. During this soaking period, Al and N disassociate from the exterior wall 603 of the AlN charge body 601, as generally indicated by 801, along with the chemical driving agent 802, as shown in
In various aspects, the thermal and chemical driving forces 803 are controlled by the internal thermal fields as moderated by the thermal insulation 705, the susceptor 701 placement and the characteristics of the induction coil 703, such as placement, coil length, and coil-to-coil gaping, shown in
By way of example, after soaking for approximately 30 hours, the temperature of the packed crucible 30 is decreased to below 1000° C. over a period of one hour and allowed to rest and cool to near room temperature for around three hours. After the cooling period, the reactor is evacuated to a vacuum below approximately 1×10−2 torr and backfilled/purged with nitrogen until an approximate atmosphere pressure is reached and the packed crucible 30 is removed.
In various embodiments, a precursor compound or compounds that will produce the desired chemical driving agent or agents in situ maybe used to promote preferential volumetric growth. For example, Gases, solids, open porous volume foams, powders, liquids, phase changing systems, or any other volatile or nonvolatile compound containing the desired chemical driver agent elements can be used, including oxides. As shown in
As shown in
In one embodiment, the packed crucible 60 can be recharged with additional AlN powder and chemical driving agents 1201, as shown in
The nucleation of the crystals grown may be further controlled by various configurations of the charge body 601 or the use of additional features such as the use of multiple chemical driving agents. In one embodiment, the nucleation of crystals grown from an AlN charge body may be modified by the use of a charge body having at least one layer composed of particles that differ from the particle size of an adjacent layer with different chemical driving agents in each layer. For example, an AlN body 601 may be composed of two particle sizes with carbon mixed within particles of one size and indium mixed within the particles of the second size. In this example, a single layer, similar to layer 1203, as shown in
In another embodiment, as shown in
In yet another embodiment, shown in
In one embodiment, the inert filler may be a porous body 1301 that defines one or more holes, apertures, or slits to permit chemical driving agent gas diffusion and provide desired crystal growth locations. The porous body 1301 may be positioned to contact the interior surface 411 of the charge body 601 or may be disposed within the charge body and may include apertures that may be randomly positioned or arranged in a desired orientation. Additionally, the size of the apertures may be varied.
In one embodiment, as shown
In various other embodiments, c-plane oriented AlN crystals may be grown using Aluminum Chlorides (AlClx) diffused through a substantially/sufficiently porous charge body 1605 of AlN powder which contacts cross-flowing ammonia (NH3) and chemical driving agent gases.
The crucible 1602 including the AlN charge body 1605 is placed in a high temperature reactor, such as an induction reactor, for example. In this example, a high temperature induction reactor, similar to the reactor 70 shown in
A driving force 803, defined, at least in part, by the pressure of the AlCl 1603 gas is established inside the crucible and across the AlN charge body such that the AlCl gas driven to diffuse through the charge body and into the interior cavity 1611 of the crucible 1602. In one aspect, the diffusion of the AlCl is controlled by the pressure differential between the AlCl gas and the internal pressure of the reactor. The AlCl is diffused through the AlN charge body 1605 to the internal surface 1613 where the AlCl reacts with the NH3 and chemical driving agents to preferentially freely nucleated AlN crystals on the internal surface. In another aspect, the AlN powder particle size and packing density of the AlN charge body 1605 impact the initial nucleation and subsequent growth of AlN crystals on the internal sidewalls 1613. After eight hours, the crucible 1602 is cooled down to below 1000° C. over one hour and allowed to rest for around three hours. After such time the reactor is evacuated less than 1×10−2 torr, backfilled/purged with nitrogen to atmosphere pressure, where the crucible 1602 is then removed. In this embodiment, approximately 50-500 crystals ranging in diameter from about eight mm to about fifteen mm are produced.
Referring now to
Referring now to
In another embodiment, large c-plane oriented AlN crystals may be grown using a charge body 601 composed of a mixture of AlN and tungsten (W) powder with an external supply of carbon bearing gas. In this embodiment, c-plane AlN crystals larger than 1-30 mm in diameter are controllability grown on the interior surface of the AlN/W charge body using diffused Al and nitrogen through the porous charge body reacting with an atmosphere of carbon bearing gas. AlN powder having particles in range from about 0.1 microns to 1 mm in diameter is mixed with W powder having particles in a range from about 0.1 microns to 1 mm. The distribution of the AlN and the W powder can be a random mix or preferentially orientated. In one embodiment, the concentration of chemical driving agent gases can be varied during the growth to control the volumetric growth as the source AlN powder is depleted and the growth rate of the c-plane crystals changes with time.
In yet another embodiment, large c-plane oriented AlN crystals may be grown using a charge body 601 composed of a mixture of AlN and Aluminum (Al) powder and Al2C3 powder. In this embodiment, c-plane AlN crystals larger than 1-30 mm in diameter are controllability grown on the interior surface 411 of the AlN/W charge body using diffused Al and nitrogen through the porous charge body. AlN powder having particles in range from about 0.1 microns to 1 mm in diameter is mixed with Al powder having particles in a range from about 0.1 microns to 1 mm and Al2C3 powder having particles in a range from about 0.1 microns to 1 mm. The distribution of the AlN, the Al, and the Al2C3 powder can be a random mix or preferentially orientated. In one embodiment, similar to that described in reference to
In various other embodiments, the reactor configuration shown in
Similarly, in another embodiment c-plane oriented GaN crystal may be grown via the diffusion of Ga and N species through a porous charge body composed of a GaN/In powder mix, where the In powder functions as an a chemical driving agent to enhance volumetric growth.
Referring now to
The embodiments disclosed herein may be used to manufacture c-plane oriented AlxGa1-xN crystals via HVPE growth using AlClx, GaClx, NH3, and a hydrocarbon gas as a chemical driving agent that is used to control preferential volumetric growth. Similarly, the systems and methods may be used to manufacture m-plane oriented AlxGa1-xN crystal with HVPE growth using AlClx, GaClx, NH3, and a boron gas as a chemical driving agent that is used to control preferential volumetric growth. Additionally, the embodiments disclosed herein may be used to manufacture c-plane oriented Gallium nitride crystals using NH3 and cyanide gas, used as an agent that is used to control preferential volumetric growth, diffused through a first substantially/sufficiently porous plate of Al2O3 and a second substantially/sufficiently porous body of Gallium nitride
Referring now to
Alternatively in another embodiment, shown in
Those skilled in the art will appreciate that variations from the specific embodiments disclosed above are contemplated by the invention. The invention should not be restricted to the above embodiments, but should be measured by the following claims.
The application claims priority to U.S. Provisional Application No. 61/888,414, entitled “Preferred Volumetric Enlargement Of III-Nitride Crystals,” filed on Oct. 8, 2013; and is a continuation in-part to U.S. patent application Ser. No. 14/477,431, entitled “Bulk Diffusion Crystal Growth Process,” filed on Sep. 4, 2014, which claims priority to U.S. Provisional Application No. 61/873,729, entitled “Bulk Diffusion Crystal Growth Process,” filed on Sep. 4, 2013; each of which is incorporated herein by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 61888414 | Oct 2013 | US |
