TW200531309A - Structure of light emitting diode - Google Patents

Abstract

A structure of light emitting diode comprises a semi-conductive layer, a first electrode and a second electrode, wherein the semi-conductive layer comprises a first type-doping semi-conductive layer, a second type-doping semi-conductive layer and an emitting layer. The emitting layer is located on the partial area of the first type-doping semi-conductive layer, and the second type-doping semi-conductive layer is located on the emitting layer. Besides, the first electrode is located on the first type-doping semi-conductive layer, which the emitting layer is not on. And the second electrode is located on the second type-doping semi-conductive layer. In addition, the emitting layer comprises a plurality of different quantum wells (multiple quantum wells or single quantum wells), and these different quantum wells are mutual staggered.

Description

200531309 (1) Description of the invention: The technical field to which the invention belongs belongs to a light emitting diode structure, and more particularly to a light emitting layer having different quantum well structures (multiple quantum wells or single quantum wells) interlaced with each other Light-emitting diode structure. In recent years, due to the continuous improvement of the luminous efficiency of light-emitting diodes, light-emitting diodes have gradually replaced fluorescent lamps and incandescent light bulbs in certain fields, such as scanner light sources that require high-speed response, backlight sources for liquid crystal displays, or Front-light vehicle dashboard lighting, traffic lights, and general lighting. Compared with traditional light bulbs, light-emitting diodes have absolute advantages, such as small size, long life, low voltage / current drive, not easy to break, no significant thermal problems when emitting light, no mercury (no pollution problems), and good luminous efficiency ( Power saving) and other characteristics. The use of gallium nitride-containing compound semiconductors, such as gallium nitride (GaN), gallium nitride (GaAIN), indium gallium nitride (GalnN), and other light-emitting diode elements has attracted the attention of many people. The nitrogen-containing m-v compound is a material with a wide band energy gap, and its emission wavelength can be covered from ultraviolet light to red light, so it can be said to cover almost the entire visible light band. In the current conventional technique, the light mixing method of the light emitting diode is as shown in FIG. 1 ', which is a schematic cross-sectional view of a conventional light mixing light emitting diode structure. Please refer to FIG. 1. The light emitting diode structure 10 includes a semiconductor layer 110, a first electrode 120, and a second electrode 130. The semiconductor layer 110 includes at least a first type doped semiconductor layer 112, a first The second type doped semiconductor layer 116 and a light emitting layer 114. The aforementioned light emitting layer 114 is located on the first type doped semiconductor layer 112, the second type doped semiconductor layer 116 12277twf.doc 5 200531309 is located on the light emitting layer 114, and the first electrode 120 is electrically connected to the first type doped semiconductor layer. The hetero-semiconductor layer 112 is on a partial region, and the second electrode 130 is on a part of the second-type doped semiconductor layer 116. In the conventional technology, the light emitting layer 114 of the white light-emitting diode is composed of a first multiple quantum well structure 114a and a second multiple quantum well structure 114b. The first multiple quantum well structure 114a is suitable for emitting light. Yellow light, and the second multiple quantum well structure 114b is adapted to emit blue light. When the yellow light emitted by the first multiple quantum well structure 114a is mixed with the blue light emitted by the second multiple quantum well structure 114b, Shows white light. Following the above, the material of the first electrode 120 is titanium / aluminum alloy, and the like, and the second electrode 130 includes an N-type transparent conductive oxide layer and a P-type transparent conductive oxide layer. The material of the N-type transparent conductive oxide layer is ITO and P-type transparent. The material of the conductive oxide layer is CuA102. When an applied voltage is applied between the first electrode 120 and the second electrode 130 of the light emitting diode structure 10, the carriers passing through the first multiple quantum well structure 114a and the second multiple quantum well structure 114b are caused by The quantum well structure emits light. Since the color temperature of the white light displayed by the light emitting layer 114 is determined by the first multiple quantum well structure 114a and the second multiple quantum well structure 114b, the first multiple quantum well structure U4a and the second multiple quantum well structure 114b The combination is very important. However, the design usually needs to meet many different requirements. For white light-emitting diodes, if it is simply adjusted by the combination of the first multiple quantum well structure 114a and the second multiple quantum well structure 1Hb, The color temperature and color rendering of white light can only be adjusted in a very limited range, and it is difficult to obtain white light with a lower color temperature. SUMMARY OF THE INVENTION 12277twf.doc 6 200531309 In view of this, the object of the present invention is to provide a light-emitting diode structure whose light-emitting layer has a plurality of different quantum well structures (multiple quantum wells or single quantum wells) interlaced with each other, so that the current flows in After passing through these different quantum well structures, a plurality of lights of different wavelengths can obtain white light with an appropriate color temperature after mixing. In order to achieve the above object of the present invention, the present invention provides a light emitting diode structure, which includes a semiconductor layer, a first electrode, and a second electrode, wherein the semiconductor layer includes at least a first type doped semiconductor layer, a The second type doped semiconductor layer and a light emitting layer are located on a partial region of the first type doped semiconductor layer, and the second type doped semiconductor layer is located on the light emitting layer. In addition, the light emitting layer also includes a plurality of first multiple quantum well structures and a plurality of second multiple quantum well structures, and the first multiple quantum well structure and the second multiple quantum well structure are interlaced with each other. In addition, the first electrode is located on the first type doped semiconductor layer outside the light emitting layer distribution area, and the second electrode is located on the second type doped semiconductor layer. According to a preferred embodiment of the present invention, in the above-mentioned light-emitting diode structure, the material of the second electrode includes an N-type transparent conductive oxide layer or a P-type transparent conductive oxide layer. Based on the above, the present invention adopts a light emitting diode structure having a plurality of light emitting layers with different quantum well structures (multiple quantum wells or single quantum wells) interlaced, so that when a current passes through these different quantum well structures, a variety of Light of different wavelengths can obtain white light with lower color temperature after mixing. In order to make the above-mentioned objects, features, and advantages of the present invention more comprehensible, 12277twf.doc 7 200531309, a preferred embodiment is exemplified below, and it will be described in detail with the accompanying drawings. Embodiment [First Embodiment] Please refer to FIG. 2, which illustrates a schematic cross-sectional view of a light emitting diode structure according to a first embodiment of the present invention. The light-emitting diode structure of the present invention includes a semiconductor layer, a first electrode 220, and a second electrode 230. The semiconductor layer 210 includes at least a first-type doped semiconductor layer 212 and a second-type doped semiconductor layer. 216, and a light emitting layer 214. Each film layer will be described below. In this embodiment, the light emitting layer 214 is located on the first type doped semiconductor layer 212, the second type doped semiconductor layer 216 is located on the light emitting layer 214, and the first electrode 220 is electrically connected to the first type doped semiconductor. The second electrode 230 is located on a partial region of the layer 212, and the second electrode 230 is located on a partial region of the second-type doped semiconductor layer 216. It should be noted that the light-emitting layer 214 in this embodiment is composed of a plurality of first multiple quantum well structures 214a and a plurality of second multiple quantum well structures 214b, and the first multiple quantum well structures 214a and The second multiple quantum well structures 214b are arranged alternately with each other. In addition, the first multiple quantum well structure 214a of this embodiment is suitable for emitting yellow light, and the second multiple quantum well structure 214b is suitable for emitting blue light, for example. After the carriers pass through the first multiple quantum well structure 214a and the second multiple quantum well structure 214b which are alternately arranged with each other, since the multiple quantum well structure 214a and the second multiple quantum well structure 214b are in a multiple-to-many relationship, These types are arranged alternately with each other, so overall, the white light color temperature, color rendering, and even color temperature adjustability presented by this architecture are very good. In this embodiment, the material of the first electrode 220 is, for example, Ti / Ab Ti / Al / Ti / Au, Ti / NiAl / N 彳 / Alm, or Ti / NiAl / Cr / Au. 12277twf.doc 8 200531309 In this embodiment, the material of the second electrode 230 is, for example, Ni / Au, Ni / Pt, Ni / Pd, Ni / Co, Pd / Au, Pt / Au, Ti / Au, Cr / Au, Sn / Au, Ta / Au, TiN, TiWNx, or WSix. In addition, the material of the second electrode 230 may also be an N-type transparent conductive oxide layer or a P-type transparent conductive oxide layer, and the material of the N-type transparent conductive oxide layer is, for example, ITO, CTO, ZnO: A, ZnGa204, Sn02: Sb, Ga203: Sn, AgIn〇2: Sn or In203: Zn, and the material of the P-type transparent conductive oxide layer is, for example, CuA102, LaCuOS, NiO, CnGa02, or SrCu202. [Second embodiment] Please refer to FIG. 3, which A schematic cross-sectional view of a light emitting diode structure according to a second embodiment of the present invention is shown. Compared with the light-emitting diode structure 20 of the first embodiment, in the light-emitting diode structure 30 of this embodiment, the light-emitting layer 314 is composed of a plurality of first single quantum well structures 31 and a plurality of second single quantum well structures. The structure 314b is composed of a first single quantum well structure 314a and a second single quantum well structure 314b. In addition, the first single quantum well structure 314a of this embodiment is suitable for emitting yellow light, and the second single quantum well structure 314b is suitable for emitting blue light, for example. After the carriers pass through the first single quantum well structure 314a and the second single quantum well structure 314b arranged alternately with each other, since the first single quantum well structure 314a and the second single quantum well structure 314b are multiple to multiple The types of the sensors are staggered with each other, so overall, the white light color temperature, color rendering, and even the adjustable color temperature are very good. The above-mentioned light-emitting diode structure of the present invention is not used to limit the type and number of quantum wells. The present invention can also alternately arrange three or more kinds of quantum well structures (multiple quantum wells and single quantum wells), In addition, the present invention can also adopt quantum well structures (multiple quantum wells and single quantum wells) suitable for emitting colors such as red light, green light, and blue light, and arrange them alternately. 12277twf.doc 9 200531309 In summary, the light-emitting diode structure of the present invention has at least the following advantages: 1. The light-emitting diode of the present invention has a plurality of different quantum well structures (multiple quantum wells or single quantum wells) due to its use. ), And these quantum well structures are staggered with each other, so carriers can emit light of different wavelengths after these different quantum well structures, and light of various wavelengths can get lower color temperature after mixing light. White light. 2. The light-emitting diodes of the present invention are excellent in color rendering and adjustability of color temperature because they employ a plurality of different quantum well structures and stagger these quantum well structures. Although the present invention has been disclosed above in a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and retouches without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application. [Brief description of the drawings] FIG. 1 is a schematic cross-sectional view of a conventional mixed light-emitting light emitting diode structure. Fig. 2 is a schematic cross-sectional view showing a light emitting diode structure according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a light emitting diode structure according to a second embodiment of the present invention. [Schematic description] 10, 20, 30: Light-emitting polar structure 110, 2〗 〇, 310 · Semiconductor layer 12277twf.doc 10 200531309 112, 212, 312: Type I doped semiconductor layers 114, 214 , 314: light emitting layers 114a, 214a: first multiple quantum well structure 114b, 214b: second multiple quantum well structure 116, 216, 316: second type doped semiconductor layer 120, 220, 320: first electrode 130 , 230, 330: second electrode 314a: first single quantum well structure 314b: second single quantum well structure 11 12277twf.doc

Claims (1)

200531309 Scope of patent application: 1. A light-emitting diode structure including: a substrate; a crystal core layer on the substrate; a buffer layer on the crystal core layer; a first restraint Layer, located on a partial region of the buffer layer, wherein the doping type of the first binding layer is the same as the doping type of the buffer layer; a light emitting layer, located on the first binding layer, wherein the light emitting layer includes A plurality of first multiple quantum well structures and a plurality of second multiple quantum well structures, and the first multiple quantum well structures and the second multiple quantum well structures are interlaced with each other; a second binding layer, Located on the light-emitting layer, wherein the doping type of the second binding layer is different from that of the first binding layer; a contact layer is located on the second binding layer; a first electrode is located on the The buffer layer is outside the first binding layer distribution area; and a second electrode is located on the contact layer. 2. The light-emitting diode structure described in item 1 of the scope of the patent application, wherein the material of the substrate includes alumina, silicon carbide (SiC), zinc oxide (ZnO), silicon (Si), and gallium phosphide (GaP ) And gallium arsenide (GaAs). 3. The light-emitting diode structure according to item 1 of the scope of the patent application, wherein the material of the crystal core layer includes AlelnfOa ^^, 〇 分 + 于. 4. The light-emitting diode structure as described in item 3 of the patent application scope, wherein the 12277twf.doc 12 200531309 crystal core layer is N-type doped. 5. The light-emitting diode structure described in item 1 of the scope of the patent application, wherein the material of the buffer layer includes AlJUdGa ^ N /, 0; 0Sc + d < l. 6. The light-emitting diode structure described in item 5 of the scope of patent application, wherein the buffer layer is N-type doped. 7. The light-emitting diode structure described in item 1 of the scope of the patent application, wherein the material of the first binding layer includes A1χΙτν ^ _χ_γN, χ, at 0; (Kx + y <l; x > c. 8. The light emitting diode structure described in item 1 of the scope of the patent application, wherein the first multiple quantum well structures include doped AlJiibGa ^ bN / AlJiiyGa ^ yN, and a, b >0; (Ka + b < l x, y ^ 〇 ·, 〇 立 ·, 'and the second multiple quantum well structures include doped AytihGauhN / AUtiyGa ^ yN, and g, feO; 0 < g + h <l; X, y >0; 0 < x + y <l; x > c > g 0 9. The light-emitting diode structure described in item 1 of the scope of patent application 'wherein the light-emitting layer is N-type doped. 10. According to the scope of patent application The light-emitting diode structure according to item 1, wherein the light-emitting layer is P-type doped. 11. The light-emitting diode structure according to item 1 of the patent application scope, wherein the first multiple quantum well structures Including undoped AlJnbGa ^ bN / AlJiiyGa ^ yN, and a, b >0; 0Sa + b <l; x, y20; (Kx + y <l; x> c> a, and the second multiple Quantum well structure including undoped Ayr ihGa ^ hN / AyHyGa ^ yN, and g, feO; 0 < g + h <l; x, y2〇; 〇 < x + y <l; x > c> g. 12. As the first item of the scope of patent application The light-emitting diode structure, wherein the material of the second binding layer includes AlJnyGa ^ yN #, at 0; (Kx + y <l; x > c.) 13. As described in item 1 of the scope of patent application Light-emitting diode structure, wherein the material of the first electrode includes Ti / A, TVAl / Ti / Au, Ti / Al / Pt / Au, Ti / Al / Ni / Au, 12277twf.doc 13 200531309 Ti / Al / Pd / Au, Ti / Al / Cr / Au, Ti / Al / Co / Au, Cr / Au, Cr / Pt / Au, Cr / Pd / Au, Cr / Ti / Au ^ Cr / TiWx / Au ^ Cr / Al / Cr / Au ^ Cr / Al / Pt / Au > Cr / Al / Pd / Au ^ Cr / Al / Ti / Au ^ Cr / Al / Co / Au ^ Cr / Al / Ni / Au ^ Pd / Al / Ti / Au > Pd / Al / Pt / Au ^ Pd / Al / Ni / Au, Pd / Al / Pd / Au, Pd / Al / Cr / Au, Pd / Al / Co / Au, Nd / Al / Pt / Au, Nd / Al / Ti / Au ^ Nd / Al / Ni / Au ^ Nd / Al / Cr / Au 'Nd / Al / Co / A > Hf / Al / Ti / Au ^ Hf / Al / Pt / Au, Hf / Al_Au, Hf / Al / P, u, Hf / Al / Cr / Au, Hf / Al / Co / Au, Zr / Al / Ti / Au > Zr / Al / Pt / Au ^ Zr / Al / Ni / Au 'Zr / Al / Pd / Au ^ Zr / Al / Cr / Au ^ Zr / Al / Co / Au, TiNx / Ti / Au, TiNx / Pt / Au, TiNx ^ / Au, TiNx / Pd / Au, TiNx / Cr / Au, TiNx / Co / Au, TiWNx / Ti / Au, TiWNx / Pt / Au, TiWNx / Ni / Au, TiWNx / Pd / Au, TiWNx / Cr / Au, TiWNx / Co / Au, NiAl / Pt / Au, One of NiAl / Cr / Au, NiAl / Ni / Au, NiAl / Ti / Au, TVNiAl / Pt / Au, Ti / NiAl / Ti / Au, TVNiAl / Ni / Au, Ti / NiAl / Cr / Au. 14. The light-emitting diode structure according to item 1 of the scope of the patent application, wherein the material of the second electrode includes Ni / Au, Ni / Pt, Ni / Pd, Ni / Co, Pd / Au, Pt / Au, Ti / Au, Cr / Au, Sn / Au, Ta / Au, ΉΝ, 丁 丨 \ ¥ 凡, and WSix. 15. The light-emitting diode structure as described in item 1 of the scope of the patent application, wherein the material of the second electrode includes one of an N-type transparent conductive oxide layer and a P-type transparent conductive oxide layer-〇16. The light-emitting diode structure according to item 15 of the patent, wherein the N-type transparent conductive oxide layer includes IT0, CT0, Zn0: Al, ZnGa204, Sn02: Sb, Ga203: Sn, AgIn02: Sn, and ln203: Zη One. Π. The light-emitting diode structure according to item 15 of the scope of the patent application, wherein the P-type transparent conductive oxide layer includes one of CuA102, LaCuOS, NiO, CuGa02 | ^ SrCu202. 18 · —A kind of light emitting diode structure, including: 12277twf.doc 14 200531309 a semiconductor layer, the semiconductor layer includes at least a first type doped semiconductor layer, a second type doped semiconductor layer, and a light emitting layer, the The light emitting layer is located on a partial region of the first type doped semiconductor layer, and the second type doped semiconductor layer is located on the light emitting layer, wherein the light emitting layer includes a plurality of first multiple quantum well structures and a plurality of A second multiple quantum well structure, and the first multiple quantum well structures and the second multiple quantum well structures are interlaced with each other; a first electrode, the first type located outside the light emitting layer distribution area; On the doped semiconductor layer; and a second electrode on the second type doped semiconductor layer. 19. The light-emitting diode structure according to item 18 of the scope of patent application, wherein the material of the first electrode includes Ti / A, Ti / Al / Ti / Au, Ti / Al / Pt / Au, Ti / Al / Ni / Au, Ti / Al / Pd / Au ^ Ti / Al / Cr / Au 'Ti / Al / Co / Au > Cr / Au ^ Cr / Pt / Au > Cr / Pd / Au' Cr / Ti / Au > Cr / TiWx / Au ^ Cr / Al / Cr / Au ^ Cr / Al / Pt / Au ^ Cr / Al / Pd / Au > Cr / Al / Ti / Au, Cr / Al / Co / Au, Cr / A picture / Au, P_ / Ti / Au, Pd / Al / Pt / Au, Pd / Al / Ni / Au, Pd / Al / Pd / Au, Pd / Al / Cr / Au, Pd / Al / Co / Au, Nd / Al / Pt / Au, N series / Ti / Au, N bump / Ni / Au, Nd / Al / Cr / Au, Nd / Al / Co / A, Hf / Al / Ti / Au, Hf / Al / Pt / Au > Hf / Al / Ni / Au 'Hf / Al / Pd / Au ^ Hf / Al / Cr / Au > Hf / Al / Co / Au > Zr / Al / Ti / Au > Zr / Al / Pt / Au ^ Zr / Al / Ni / Au ^ Zr / Al / Pd / Au > Zr / Al / Cr / Au ^ Zr / Al / Co / Au, TiNx / Ti / Au, TiNx / P steal, TiNx_ / Au, TiNx / Pd / Au, TiNx / Cr / Au, TiNx / Co / Au, TTiWN / Ti / Aii, TiWNx / Pt / Au, TiWNx / Ni / Au, TiWNx / Pd / Au, TiWNx / Cr / Au, TiWNx / Co / Au, NiAl / Pt / Au, NiAl / Cr / Au, NiAl / Ni / Au, NiAl / Ti / Au, Ti / NiAl / Pt / Au, TVNiAl / Ti / Au, Ti / NiAl / Ni / Au, Ti / NiAl / Cr / Au. 12277twf.doc 15 200531309 20 · The light-emitting diode structure described in item 18 of the scope of patent application, wherein the material of the second electrode includes Ni / Au, Ni / Pt, Ni / Pd, Ni / Co, Pd / Au , Pt / Au, Ti / Au, Cr / Au, Sn / Au, Ta / Au, TiN, TiWNx, and WSix. 21. The light-emitting diode structure according to item 18 of the scope of the patent application, wherein the material of the second electrode includes one of an N-type transparent conductive oxide layer and a P-type transparent conductive oxide layer. 22. The light-emitting diode structure according to item 21 of the scope of patent application, wherein the N-type transparent conductive oxide layer includes IT0, CT0, Zn0: Al, ZnGa204, Sn02: Sb, Ga203: Sn, AgIn02: Sn, and In2 〇3: One of Zn. 23. The light-emitting diode structure according to item 21 of the application, wherein the P-type transparent conductive oxide layer includes one of CuAK) 2, LaCuOS, NiO, CuGa02, and SrCu202. 24. A light emitting diode structure comprising: a semiconductor layer, the semiconductor layer including at least a first type doped semiconductor layer, a second type doped semiconductor layer, and a light emitting layer, the light emitting layer is located in the The first type doped semiconductor layer is on a partial region, and the second type doped semiconductor layer is located on the light emitting layer, wherein the light emitting layer includes a plurality of first single quantum well structures and a plurality of second single quantum well structures. And the first single quantum well structures and the second single quantum well structures are mutually staggered; a first electrode is located on the first type doped semiconductor layer outside the light emitting layer distribution area; and a first Two electrodes are located on the second type doped semiconductor layer. 25. The light-emitting diode structure described in item 24 of the scope of patent application, wherein 12277twf.doc 16 200531309 The material of the first electrode includes 1VA Ti / Al / Ti / Au, Ti / Al / Pt / Au, Ti / Al / Ni / Au, Ti / Al / Pd / Au, Ti / Al / Cr / Au, Ti / Al / Co / Au, Cr / Au, Cr / Pt / Au, Cr / Pd / Au, Cr / Ti / AU, Cr / TiWx / Au, Cr / Al / Cr / Au, Cr / Al / Pt / Aii, Cr / Al / Pd / Aii, Cr / Al / Ti / Au, Cr / Al / Co / Au, Cr / Al / Ni / Au, Pd / Al / Ti / Au, Pd / Al / Pt / Au, Pd / Al / Ni / Au, Pd / Al / Pd / Au, Pd / Al / Cr / Au, Pd / Al / Co / Au, Nd / Al / Pt / Au, Nd / Al / Ti / Au 'Nd / Al / Ni / Au ^ Nd / Al / Cr / Au > Nd / Al / Co / A > Hf / Al / Ti / Au > Hf / Al / Pt / Au 'Hf / Al / Ni / Au ^ Hf / Al / Pd / Au ^ Hf / Al / Cr / Au ^ Hf / Al / Co / Au' Zr / Al / Ti / Au ^ Zr / Al / Pt / Au ^ Zr / Al / Ni / Au > Zr / Al / Pd / Au > Zr / Al / Cr / Au ^ Zr / Al / Co / Au 'TiNx / Ti / Au ^ TiNx / Pt / Au 'TiNx / Ni / Au' TiNx / Pd / Au 'TiNx / Cr / Au' TiNx / Co / Au 'TiWNx / Ti / Au' TiWNx / Pt / Au 'TiWNx / Ni / Au ^ TiWNx / Pd / Au, TiWNx / Cr / Au, TiWNx / Co / Au, NiAl / Pt / Au, NiAl / Cr / Au, NiAl / Ni / Au, NiAl / TVAu, Ti / NiAl / Pt / Au, Ti / NiAl / Ti / Au, Ti / Ni Al / Ni / Au, Ti / NiAl / Cr / Au. 26. The light-emitting diode structure described in item 24 of the scope of patent application, wherein the material of the second electrode includes Ni / Au, Ni / Pt, Ni / Pd, Ni / Co, Pd / Au, Pt / Au, One of Ti / Au, Cr / Au, Sn / Au, Ta / Au, TiN, TiWNx, and WSix. 27. The light-emitting diode structure according to item 24 of the scope of the patent application, wherein the material of the second electrode includes one of an N-type transparent conductive oxide layer and a P-type transparent conductive oxide layer. 28. The light-emitting diode structure described in item 27 of the scope of patent application, wherein the N-type transparent conductive oxide layer includes IT0, CT0, Zn0: Al, ZnGa204, Sn02: Sb, Ga203: Sn, AgIn02: Sn, and In203 : Zn One of them. 29. The light-emitting diode structure according to item 27 of the scope of the patent application, wherein the P-type transparent conductive oxide layer includes one of CuA102, LaCuOS, NiO, CuGa02, and SrCu202. 12277twf.doc 17