Embodiments of this disclosure relate generally to semiconductor devices and, more specifically, to a vertical-cavity surface-emitting laser (VCSEL) device and photodiode and methods of forming the same.
Semiconductor devices can be a reliable, efficient, compact, and inexpensive means for generating light and detecting light, such as semiconductor lasers and photodiodes. As a result, there are many commercial, industrial, and scientific applications for light-emitting and light-detecting semiconductor devices. Such applications include telecommunications, compact disk and laser disk players, high-speed printers, and augmented reality (AR) and virtual reality (VR) systems, among others.
In many applications that rely on semiconductor lasers and photodiodes, compactness is an important consideration. For instance, AR/VR headsets are designed to perform complex operations within the confined space of a head-mounted device, such as the presentation of stereoscopic video and the precise tracking of head and eye motion. Therefore, a typical AR/VR headset includes a large number of sensors, optics, light sources, and electronic devices that must all be contained within a compact and light-weight assembly. Due to their small size and high performance and reliability, semiconductor lasers are commonly employed as light sources for the projection modules of AR/VR headsets, while photodiodes monitor the optical output of such projection modules for eye safety.
One disadvantage of conventional semiconductor lasers and photodiodes is that they can be problematically large for certain space-sensitive applications, even though the active area of such devices is quite small. For instance, an accurate, high-responsivity photodiode may have an active area that is approximately 0.1 mm in diameter, while the diameter of the entire photodiode package can be dozens of times larger (e.g., 5 mm or more). Similarly, a vertical-cavity surface-emitting laser (VCSEL) that is commonly employed as a light source for AR and VR devices can have a package diameter that is several times larger than the active area of the VCSEL. As a result, use of conventional semiconductor lasers and photodiodes can be difficult to implement in space-sensitive systems without increasing the overall size of the system.
As the foregoing illustrates, what is needed in the art are more effective techniques for fabricating semiconductor lasers and photodiodes.
One embodiment of the present disclosure sets forth a light-emitting device that includes: a single die formed from a portion of a semiconductor substrate of a first conductivity type, a first vertical cavity surface-emitting laser (VCSEL) that is formed from a set of material layers disposed on a surface of the portion of the semiconductor substrate, and a first photodiode that is formed at the surface of the portion of the semiconductor substrate.
One advantage of the design disclosed herein is that one or more semiconductor lasers and one or more photodiodes can be formed together on a single die. Consequently, a device having the functionality of a laser and the functionality of a photodiode can be implemented in a single packaged semiconductor device that is much smaller than a laser and a photodiode that are packaged separately. A further advantage of the disclosed design is that a system can be fabricated with fewer individual components, thereby reducing the potential for supply chain constraints affecting fabrication of the system. That is, there are fewer components that, due to lack of availability, can prevent fabrication of the system. These technical advantages represents one or more technological advancements over prior art approaches.
So that the manner in which the above recited features of the various embodiments can be understood in detail, a more particular description of the disclosed concepts, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the disclosed concepts and are therefore not to be considered limiting of scope in any way, and that there are other equally effective embodiments.
For clarity, identical reference numbers have been used, where applicable, to designate identical elements that are common between figures. It is contemplated that features of one embodiment may be incorporated in other embodiments without further recitation.
In the following description, numerous specific details are set forth to provide a more thorough understanding of the various embodiments. However, it is apparent to one of skilled in the art that the disclosed concepts may be practiced without one or more of these specific details.
Embodiments described herein may include or be implemented in conjunction with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, for example, a virtual reality (VR) system, an augmented reality (AR) system, a mixed reality (MR) system, a hybrid reality system, or some combination and/or derivatives thereof. Artificial reality content may include, without limitation, completely generated content or generated content combined with captured (e.g., real-world) content. The artificial reality content may include, without limitation, video, audio, haptic feedback, or some combination thereof. The artificial reality content may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional effect to the viewer). Additionally, in some embodiments, artificial reality systems may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, e.g., create content in an artificial reality system and/or are otherwise used in (e.g., perform activities in) an artificial reality system. The artificial reality system may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.
In the embodiment illustrated in
VCSEL 110 is a semiconductor laser that, like a light-emitting diode, can convert electrical energy into light. Through the process of stimulated emission, VCSEL 110 generates light with the same phase, coherence, and wavelength. More specifically, VCSEL 110 is a surface-emitting lasers (SELs), which outputs radiation perpendicular to the plane of the semiconductor substrate from which VCSEL 110 is formed. For AR and VR devices in particular, VCSELs are commonly employed as a light source. In a VCSEL, the “vertical” direction indicates a direction perpendicular to the plane of the semiconductor substrate on which the constituent layers are epitaxially grown or deposited, where “up” refers to the direction that such layers are grown or deposited and down refers to the direction toward the semiconductor substrate. VCSELs have many advantages over edge-emitting lasers, such as low threshold current, single longitudinal mode, a circular output beam profile, ease of fiber coupling, and scalability to monolithic laser arrays. For example, a large number of VCSELs (e.g., hundreds or thousands) can be fabricated on a single semiconductor die, such as substrate portion 101.
In the embodiment illustrated in
In alternative embodiments, VCSEL 110 is configured as a multi-junction VCSEL. In such embodiments, VCSEL 110 includes multiple quantum well layers and a tunnel junction layer that is disposed between the quantum well layers that are all disposed in laser cavity 118.
As shown in
To enable operation of VCSEL 110, VCSEL 110 includes top metallization 117, which is electrically coupled to top mirror layer 115, and a bottom metallization 157, which is electrically coupled to substrate portion 101. Further, in the embodiment illustrated in
In the embodiment illustrated in
To enable operation of photodiode 120, photodiode 120 includes top metallization 127, which is electrically coupled to second semiconductor region 122, and bottom metallization 157. In some embodiments, top metallization 127 is configured as a metal trace (or a trace that includes some other conductive material) that transmits an output signal from photodiode 120. Top metallization 127 forms or includes a contact that is electrically coupled to second semiconductor region 122. In the embodiment illustrated in
According to various embodiments, first semiconductor region 121 is formed from or includes a portion of substrate portion 101, which is the semiconductor substrate on which VCSEL 110 is also formed. Similarly, in some embodiments, second semiconductor region 122 and intrinsic semiconductor region 123 are each formed from a different portion of substrate portion 101. In such embodiments, intrinsic semiconductor region 123, which is an intrinsic semiconductor type, is formed from a portion of substrate portion 101, which is a first conductivity type. Further, in such embodiments, second semiconductor region 122, which is a second conductivity type, is formed from a portion intrinsic semiconductor region 123, which is an intrinsic semiconductor type. In such embodiments, intrinsic semiconductor region 123 is formed from a portion of substrate portion 101 via a first ion implantation process (described below), and second semiconductor region 122 is formed from a portion of intrinsic semiconductor region 123 via a second ion implantation process (described below) that is performed after the first ion implantation process.
Alternatively, in some embodiments, photodiode 120 is configured as a P-N photodiode. In such embodiments, photodiode 120 includes first semiconductor region 121 of the first conductivity type and second semiconductor region 122 the second conductivity type, and does not include intrinsic semiconductor region 123.
In an example embodiment, top mirror layer 115 has a thickness on the order of about 2-3 microns and includes a plurality (e.g., 30 pairs) of alternating layers of gallium-arsenide (GaAs) and p-doped aluminum-gallium-arsenide (AlGaAs). In the example embodiment quantum well layer 112 includes a layer of indium-gallium-arsenide (InGaAs) having a thickness on the order of about 10-100 nanometers. In the example embodiment, ohmic contact 134 includes a highly p-doped GaAs contact layer. In the example, substrate portion 101 includes a portion of a GaAs wafer, and bottom mirror layer 111 has a thickness on the order of about 2-3 microns and includes a plurality (e.g., 15 pairs) of alternating layers of GaAs and n-doped aluminum-arsenide (AlAs). Thus, in the example embodiment, top mirror layer 115 is of a first semiconductor type and bottom mirror layer 111 is of a second semiconductor type.
In the example embodiment, photodiode 120 is configured to generate a signal in response to incident light having a wavelength between about 800 nm and 900 nm. Further, intrinsic semiconductor region 123 includes one or more implant species that cause the portion of substrate portion 101 corresponding to intrinsic semiconductor region 123 to change from the first conductivity type to an intrinsic semiconductor type. For example, in some embodiments, the implant species includes boron ions. In addition, second semiconductor region 122 includes implant species that cause the portion of intrinsic semiconductor region 123 corresponding to second semiconductor region 122 to change from an intrinsic semiconductor type to the second conductivity type. For example, in some embodiments, the implant species includes zinc ions, which is an impurity that acts as a P dopant in GaAs.
In the example embodiment described above, material layers on the bottom side (e.g., the side closest to substrate portion 101) of an active region of VCSEL 110 are described being doped to have a first conductivity type (e.g., n-type), and material layers on the top side (e.g., the side farthest from substrate portion 101) of the active region VCSEL 110 are described being doped to have a second conductivity type (e.g., p-type). In other embodiments, an opposing doping scheme may be employed for both VCSEL and photodiode 120. Alternatively, or additionally, one or more layers included in set of material layers 102 may be undoped, and/or more heavily doped than in the exemplary description above.
As shown, fabrication process 300 begins at step 301, where set of material layers 102 is formed on a semiconductor substrate 401, as shown in
In step 302, ohmic contact 134 is formed on a top region of set of material layers 102, such as an exposed surface 401 of top mirror layer 115, as shown in
In step 303, oxidation trenches 133 are formed in set of material layers 102, as shown in
In step 304, an aperture 116 is formed in set of material layers 102, as shown in
In step 305, laser cavities 118 in set of material layers 102 are isolated, as shown in
In step 306, first electrical connections (e.g., bottom contacts 137) are formed that connect bottom mirror layer 111 to a top metallization, as shown in
In step 307, second electrical connections are formed on a top region of set of material layers 102, as shown in
In step 308, a portion of set of material layers 102 is etched to expose a surface 411 of substrate portion 101, as shown in
In step 309, intrinsic semiconductor region 123 is formed from a portion of substrate portion 101 via a first ion implantation process, as shown in
In step 310, second semiconductor region 122 is formed from a portion of intrinsic semiconductor region 123 via a first second ion implantation process, as shown in
In step 311, top metallization 127 is formed on a top region of photodiode 120, as shown in
In step 312, an electrical connection to a bottom region of VCSEL 110 is formed, such as a bottom contact. For example, in the embodiment illustrated in
In step 313, substrate portion 101, along with VCSEL 110 and photodiode 120, is separated from semiconductor substrate 400, as shown in
By way of example, in the embodiments described above, VCSEL 110 is configured to emit laser light from a top surface. In other embodiments, VCSEL 110 can be configured to emit laser light from a bottom surface, for example through substrate portion 101.
In embodiments described above, an integrated semiconductor device is depicted to include a single semiconductor laser and a single photodiode that are formed on a single die. In other embodiments, an integrated semiconductor device includes an array of multiple semiconductor lasers and/or photodiodes that are formed on a single die. One such embodiment is described below in conjunction with
Because photodiodes 520 are formed on the same die as VCSELs 510, photodiodes 520 can be positioned on one or more edge regions 504 of array 502 and/or within array 502, such as at a center point of array 502 and/or between individual VCSELs 510. Thus, the functionality of photodiodes 520 is incorporated into integrated semiconductor device 500 without significantly increasing the total size of integrated semiconductor device 500 after packaging.
For reference, a conventional photodiode 550 that is enclosed in an individual package 551 is also shown in
One advantage of the techniques disclosed design disclosed herein is that one or more semiconductor lasers and one or more photodiodes can be formed together on a single die. Consequently, a device having the functionality of a laser and the functionality of a photodiode can be implemented in a single packaged semiconductor device that is much smaller than a laser and a photodiode that are packaged separately. A further advantage of the disclosed design is that a system can be fabricated with fewer individual components, thereby reducing the potential for supply chain constraints affecting fabrication of the system. That is, there are fewer components that, due to lack of availability, can prevent fabrication of the system. These technical advantages represents one or more technological advancements over prior art approaches
[Claim combinations inserted by Artegis here at time of filing].
Any and all combinations of any of the claim elements recited in any of the claims and/or any elements described in this application, in any fashion, fall within the contemplated scope of the present disclosure and protection.
The foregoing description of the embodiments of the disclosure has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.
Some portions of this description describe the embodiments of the disclosure in terms of algorithms and symbolic representations of operations on information. These algorithmic descriptions and representations are commonly used by those skilled in the data processing arts to convey the substance of their work effectively to others skilled in the art. These operations, while described functionally, computationally, or logically, are understood to be implemented by computer programs or equivalent electrical circuits, microcode, or the like. Furthermore, it has also proven convenient at times, to refer to these arrangements of operations as modules, without loss of generality. The described operations and their associated modules may be embodied in software, firmware, hardware, or any combinations thereof.
Any of the steps, operations, or processes described herein may be performed or implemented with one or more hardware or software modules, alone or in combination with other devices. In one embodiment, a software module is implemented with a computer program product comprising a computer-readable medium containing computer program code, which can be executed by a computer processor for performing any or all of the steps, operations, or processes described.
Embodiments of the disclosure may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, and/or it may comprise a general-purpose computing device selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory, tangible computer readable storage medium, or any type of media suitable for storing electronic instructions, which may be coupled to a computer system bus. Furthermore, any computing systems referred to in the specification may include a single processor or may be architectures employing multiple processor designs for increased computing capability.
Embodiments of the disclosure may also relate to a product that is produced by a computing process described herein. Such a product may comprise information resulting from a computing process, where the information is stored on a non-transitory, tangible computer readable storage medium and may include any embodiment of a computer program product or other data combination described herein.
Finally, the language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the disclosure be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the disclosure, which is set forth in the following claims.
The descriptions of the various embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations is apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Aspects of the present embodiments may be embodied as a system, method, or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a ““module” or “system.” Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.
Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
Aspects of the present disclosure are described above with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It is understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine. The instructions, when executed via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions/acts specified in the flowchart and/or block diagram block or blocks. Such processors may be, without limitation, general purpose processors, special-purpose processors, application-specific processors, or field-programmable gate arrays.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
While the preceding is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims the priority benefit of United States provisional patent application titled, “METHOD FOR FORMING AN INTEGRATED GAAS VCSEL ARRAY AND PHOTODIODE,” filed on Feb. 2, 2022, and having Ser. No. 63/305,946. The subject matter of this related application is hereby incorporated herein by reference.
Number | Date | Country | |
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63305946 | Feb 2022 | US |