Patent Application
20150034965
The present disclosure generally relates to solid state light emitting sources and, more particularly, to a light emitting diode (LED) and a method for manufacturing the LED.
LEDs have many advantages, such as high luminosity, low operational voltage, low power consumption, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness which have promoted the wide use of LEDs as a light source.
A typical LED includes a substrate, an N-type semiconductor layer, an active layer and a P-type semiconductor layer formed on the substrate in series. A part of light emitted from the active layer traverses through the P-type semiconductor layer to illuminate; the other part of light is totally reflected back into an interior of the LED by an outer surface of the P-type semiconductor layer to be wasted. Thus, the light extraction efficiency of the LED must to be improved.
Therefore, what is needed, is an LED and a method for manufacturing the LED which can overcome the limitations described above.
An LED 100 in accordance with an embodiment of the present disclosure will now be described in detail below and with reference to the drawings.
Referring to
In this embodiment, the substrate 10 is a rectangular sapphire layer, and the active layer 40 is a multiple quantum well layer. A bottom surface of the un-doped GaN layer 20 entirely covers the top surface of the substrate 10. The semiconductor structure is etched from top to bottom until a part of the P-type GaN layer 50, a part of the active layer 40, and a part of the N-type GaN layer 30 are removed and a part of the N-type GaN layer 30 is exposed. Two electrodes 60 are respectively mounted on the P-type GaN layer 50 and the exposed part of the N-type GaN layer 30.
A plurality of first holes 21 and a plurality of second holes 23 are defined in the un-doped GaN layer 20. The first holes 21 are defined along a transverse direction of the un-doped GaN layer 20 and extend through opposite sides of the un-doped GaN layer 20 at the transverse direction. The first holes 21 are spaced from each other. The second holes 23 are located above the first holes 21, defined along a longitudinal direction of the un-doped GaN layer 20 and extend through opposite ends of the un-doped GaN layer 20 at the longitudinal direction. The second holes 23 are spaced from each other. Bottom ends of the second holes 23 communicate top ends of the first holes 21. Each first hole 21 and second hole 23 is an elongated, cylindrical hole. A bottom end of the first hole 21 is coplanar with a bottom surface of the un-doped GaN layer 20 and is closed by the top surface of the substrate 10. The second holes 23 are located at a middle portion of the un-doped GaN layer 20 along a height direction of the un-doped GaN layer 20. A diameter of the first hole 21 and the second hole 23 is varied between 10 nanometer to 40 nanometer. In the depicted embodiment, the diameter of the first hole 21 is equal to that of the second hole 23 and is 20 nanometer. Air is contained in the first holes 21 and the second holes 23. Because the refractive index of the air is different from that of the un-doped GaN layer 20, light arrived at the interfaces between the un-doped GaN layer 20 and the first holes 21, and between the un-doped GaN layer 20 and the second holes 23 is reflected.
When a part of light emitted from the active layer 40 is arrived to the first holes 21 and the second holes 23, the light is reflected by the interfaces between the un-doped GaN layer 20 and the first and second holes 21, 23 several times to change the incidence angle of the light to make the light travel bias away the substrate 10 and avoid or tremendously decrease the absorption of the substrate 10. Therefore, the light extraction efficiency of the LED 100 is improved.
The present disclosure further provides a method for manufacturing the LED 100 of
Referring to
In the second step, the semiconductor structure is grown on the top surface of the substrate 10 and enclosing the first carbon nanotubes 70 and the second carbon nanotubes 80 therein. The semiconductor structure includes the un-doped GaN layer 20, the N-type GaN layer 30, the active layer 40 and the P-type GaN layer 50 grown on the top surface of the substrate 10 in series. The un-doped GaN layer 20 grows from gaps between the first carbon nanotubes 70 and the second carbon nanotubes 80 until the un-doped GaN layer 20 encloses the top ends of the second carbon nanotubes 80 to decrease lattice defect of the semiconductor structure.
In the third step, the semiconductor structure is etched from top to bottom until a part of the P-type GaN layer 50, a part of the active layer 40, and a part of the N-type GaN layer 30 are removed and a part of the N-type GaN layer 30 is exposed. The electrodes 60 are respectively mounted on the P-type GaN layer 50 and the exposed N-type GaN layer 30.
In the fourth step, the first carbon nanotubes 70 and the second carbon nanotubes 80 are removed to define the first holes 21 and the second holes 23 in the un-doped GaN layer 20. In this embodiment, the first carbon nanotubes 70 and the second carbon nanotubes 80 are radiated by laser having an energy intensity of 0.15˜10 w/cm2 to become gas. Generally, when the substrate 10 and the un-doped GaN layer 20 are radiated by larger than 4000˜5000 w/cm2 laser, the substrate 10 will be stripped from the un-doped GaN layer 20. So, when the first carbon nanotubes 70 and the second carbon nanotubes 80 are removed, the substrate 10 combines the un-doped GaN layer 20 together stably.
It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, including in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013103333276 | Aug 2013 | CN | national |
