Light emitting diode

Abstract

An AlGaInP light-emitting diode includes from bottom up a substrate, a distributed Bragg reflector (DBR) reflecting layer, an N-type semiconductor layer, a quantum well light-emitting layer, a P-type semiconductor layer, a transient layer and a P-type current spreading layer. The DBR reflecting layer is multispectral-doping. The P-type semiconductor layer includes a first P-type semiconductor layer adjacent to the quantum well light-emitting layer and a second P-type semiconductor layer adjacent to the transient layer. A doping concentration of the second P-type semiconductor layer is lower than that of the first P-type semiconductor layer. By improving doping concentration of the multispectral DBR reflecting layer, current spreading can be improved, thus improving aging performance. A concentration difference is formed with the transient layer to balance doping of the transient layer; this avoids increasing non-radiation composition from high doping of the transient layer during long-time aging.

Claims

1. An AlGaInP light-emitting diode, comprising from bottom up: a substrate; a distributed Bragg reflector (DBR) reflecting layer; an N-type semiconductor layer; a quantum well light-emitting layer; a P-type semiconductor layer; a transient layer; and a P-type current spreading layer; wherein: the DBR reflecting layer is multispectral-doping, comprising: a first DBR reflecting layer; a second DBR reflecting layer; and a third DBR reflecting layer; a doping concentration of the first DBR reflecting layer is higher than a doping concentration of the second DBR reflecting layer, and the doping concentration of the second DBR reflecting layer is higher than a doping concentration of the third DBR reflecting layer; the P-type semiconductor layer comprises: a first P-type semiconductor layer adjacent to the quantum well light-emitting layer; and a second P-type semiconductor layer adjacent to the transient layer; wherein a doping concentration of the second P-type semiconductor layer is lower than a doping concentration of the first P-type semiconductor layer; wherein a material of the P-type semiconductor layer comprises Al.sub.xIn.sub.(1-x)P, wherein 0<x<1.

2. The AlGaInP light-emitting diode of claim 1, configured to be smaller than 50 mil.sup.2, and with a drive current higher than or equal to 100 mA to improve aging performance.

3. The AlGaInP light-emitting diode of claim 1, wherein the substrate is selected from at least one of GaAs, GaP or Ge suitable for epitaxial growth.

4. The AlGaInP light-emitting diode of claim 1, wherein the doping concentration of the third DBR reflecting layer is 210.sup.18110.sup.20 cm.sup.3.

5. The AlGaInP light-emitting diode of claim 1, wherein reflection wave bands of the first DBR reflecting layer, the second DBR reflecting layer and the third DBR reflecting layer are 700-750 nm, 650-700 nm, and 600-650 nm, respectively.

6. The AlGaInP light-emitting diode of claim 1, wherein there are 2-7 pairs of the first DBR reflecting layer, 6-12 pairs of the second DBR reflecting layer, and 13-20 pairs of the third DBR reflecting layer, respectively.

7. The AlGaInP light-emitting diode of claim 1, wherein the doping concentration of the second P-type semiconductor layer is 40%-80% the doping concentration of the first P-type semiconductor layer.

8. The AlGaInP light-emitting diode of claim 1, wherein the doping concentration of the first P-type semiconductor layer is 0.710.sup.18-1.510.sup.18 cm.sup.3, and the doping concentration of the second P-type semiconductor layer is 0.2810.sup.18-1.210.sup.18 cm.sup.3.

9. The AlGaInP light-emitting diode of claim 1, wherein a thickness of the second P-type semiconductor layer is 10%-30% of a thickness of the first P-type semiconductor layer.

10. The AlGaInP light-emitting diode of claim 1, wherein a thickness of the first P-type semiconductor layer is 0.3-1.0 m, and a thickness of the second P-type semiconductor layer is 0.03-0.3 m.

11. The AlGaInP light-emitting diode of claim 1, wherein a doping concentration of the transient layer is 1.510.sup.18-4.010.sup.18 cm.sup.3.

12. The AlGaInP light-emitting diode of claim 1, wherein the transient layer adopts Al.sub.xGa.sub.yIn.sub.1-x-y P material for gradient growth of each component, wherein, 0<x<1, 0<y<1, x+y<1.

13. The AlGaInP light-emitting diode of claim 1, wherein the DBR reflecting layer adopts multi-spectral DBR, comprising a material of Al.sub.xGa.sub.1-xAs/Al.sub.yGa.sub.1-yAs, where, 0<x1, 0<y<1.

14. The AlGaInP light-emitting diode of claim 1, wherein a doping impurity of the multispectral DBR reflecting layer is any of Si, Sn, S, Se or Te.

15. The AlGaInP light-emitting diode of claim 1, wherein the doping concentration of the first DBR reflecting layer is 710.sup.18-110.sup.20 cm.sup.3; the doping concentration of the second DBR reflecting layer is 510.sup.18-110.sup.20 cm.sup.3, which is lower than that of the first DBR reflecting layer; and the doping concentration of the third DBR reflecting layer is 210.sup.18-110.sup.20 cm.sup.3, which is lower than that of the second DBR reflecting layer.

16. The AlGaInP light-emitting diode of claim 1, wherein the N-type semiconductor layer comprises Al.sub.xIn.sub.(1-x)P, where, 0<x<1.

17. The AlGaInP light-emitting diode of claim 1, wherein a doping impurity of the N-type semiconductor layer is any of Si, Sn, S, Se or Te.

18. The AlGaInP light-emitting diode of claim 1, wherein an N-type doping concentration of the N-type semiconductor layer is 0.510.sup.18-3.010.sup.18 cm.sup.3.

19. The AlGaInP light-emitting diode of claim 1, wherein a material of the quantum well light-emitting layer is Al.sub.xGa.sub.yIn.sub.1-x-yP, where 0<x<1, 0<y<1.

20. The AlGaInP light-emitting diode of claim 1, wherein: a doping impurity of the P-type semiconductor layer comprises at least one of Be, Mg, Zn, Cd, or C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are included to provide a further understanding of the disclosure and constitute a part of this specification, together with the embodiments, are therefore to be considered in all respects as illustrative and not restrictive. In addition, the drawings are merely illustrative, which are not drawn to scale.

(2) FIG. 1 shows a schematic diagram of a conventional AlGaInP light-emitting diode.

(3) FIG. 2 shows a schematic diagram of an AlGaInP light-emitting diode according to Embodiments 1 and 2 of the present disclosure.

(4) FIG. 3 shows a schematic diagram of an AlGaInP light-emitting diode according to Embodiments 3 and 4 of the present disclosure.

(5) In the drawings: 100: substrate, 110: DBR reflecting layer, 120: N-type semiconductor layer, 130: quantum well light-emitting layer, 140: P-type semiconductor layer, 150: transient layer, 160: P-type current spreading layer; 200: substrate, 210: DBR reflecting layer, 211: first DBR reflecting layer, 212: second DBR reflecting layer, 213: third DBR reflecting layer, 220: N-type semiconductor layer, 230: quantum well light-emitting layer, 240: P-type semiconductor layer, 241: first P-type semiconductor layer, 242: second P-type semiconductor layer, 250: transient layer, 260: P-type current spreading layer, 270: P electrode, 280: N electrode.

DETAILED DESCRIPTION

(6) Various embodiments of the present disclosure will be explained in details with reference to the accompanying drawings. Before further description, it should be understood, however, that various modifications and changes may be made to these embodiments. Therefore, the present disclosure is not limited to the embodiments below. It should also be noted that the scope of the present disclosure should still be subjected to the scope defined in the claims and the embodiments are merely for purposes of illustration, rather than restricting. Unless otherwise specified, all technical and scientific words shall have the same meanings as understood by persons skilled in the art.

Embodiment 1

(7) As shown in FIG. 2, this embodiment provides an AlGaInP light-emitting diode, includes process steps below: Grow a first DBR reflecting layer 211, a second DBR reflecting layer 212, a third DBR reflecting layer 213, an N-type semiconductor layer 220, a quantum well light-emitting layer 230, a P-type semiconductor layer 240, a transient layer 250 and a P-type current spreading layer 260 over the substrate 200 in successive via metal-organic chemical vapor deposition (MOCVD).

(8) In the fabrication process of the AlGaInP light-emitting diode according to the present disclosure, the carrier gas is high-purity H.sub.2, and Ga, Al, In, As, P sources are TMGa, TMAl, TMIn, AsH.sub.3 and PH.sub.3, respectively. N-type and P-type doping agents are Si.sub.2H.sub.6 and Cp.sub.2Mg, respectively. Details are as follows:

(9) First, providing a GaAs substrate.

(10) Second, deoxidizing the surface of the GaAs substrate under temperature of 650-750 C., preferably 700 C. and then inputing AsH.sub.3.

(11) Third, growing a multispectral DBR reflecting layer over the substrate, with material of Al.sub.xGa.sub.1-xAs/Al.sub.yGa.sub.1-yAs, where, 0<x1, 0<y<1, x=0, y=0.5, which includes:

(12) growing a first DBR reflecting layer 211, with reflecting wavelength of 720 nm and doping concentration of 2.010.sup.19 cm.sup.3, wherein, preferred number of pairs is 6; next, growing a second DBR reflecting layer 212 with reflecting wavelength of 670 nm and doping concentration of 1.010.sup.19 cm.sup.3, wherein, preferred number of pairs is 10; at last, growing a third DBR reflecting layer 213 with reflecting wavelength of 630 nm and doping concentration of 6.010.sup.18 cm.sup.3, wherein, preferred number of pairs is 14.

(13) Forth, growing an N-type semiconductor layer 220 over the third DBR reflecting layer 213, with preferred material of Al.sub.xIn.sub.(1-x)P, where, 0<x<1 and the doping material is Si.

(14) Fifth, growing a quantum well light-emitting layer 230 over the N-type semiconductor layer 220, wherein, the light-emitting layer material is Al.sub.xGa.sub.yIn.sub.1-x-yP, where, 0<x<1, 0<y<1.

(15) Sixed, growing a P-type semiconductor layer 240 over the quantum well light-emitting layer 230 with doping concentration of 1.010.sup.18 cm.sup.3 and preferred thickness of 0.65 m.

(16) Seventh, growing a transient layer 250 over the P-type semiconductor layer 240, wherein, the transient layer is Al.sub.xGa.sub.yIn.sub.1-x-yP, where 0<x<1, 0<y<1, x+y<1. Each component is under gradient growth.

(17) Eighth, growing a P-type current spreading layer 260 over the transient layer 250 with thickness between 2-10 m, and preferably 5 m, wherein, the material is GaP.

(18) In this new-type AlGaInP structure LED, after fabrication of the P-type electrode 270 and the N-type electrode 280, a small-size chip of 5.8 mil5.8 mil is used for evaluation. Under 100 mA and 50 C., long-term aging light attenuation value can be controlled within 8%. The performance is improved compared with that of the conventional structure (above 20%).

Embodiment 2

(19) As shown in FIG. 2, differences between Embodiment 2 and Embodiment 1 may include: with improvement of doping concentration of the multi-spectral DBR, doping concentrations of three segmentations of DBR are improved by 20% respectively, i.e., doping concentrations of the first DBR reflecting layer 211, the second DBR reflecting layer 212 and the third DBR reflecting layer 213 are 2.410.sup.19 cm.sup.3, 1.210.sup.19 cm.sup.3 and 7.210.sup.18 cm.sup.3 respectively. Other structures remain the same.

(20) In this new-type AlGaInP structure LED, after fabrication of the P-type electrode 270 and the N-type electrode 280, a small-size chip of 5.8 mil5.8 mil is used for evaluation. Under 100 mA and 50 C., long-term aging light attenuation value can be controlled within 5%. It can be seen that with improvement of DBR doping concentration, resistance to high current of small-size chip can be dramatically improved. However, this is not to say that the higher is the DBR doping, the better. Higher doping may produce impurities, thus increasing series resistance and voltage VFavg. Therefore, DBR doping concentration is controlled within 110.sup.20 cm.sup.3.

Embodiment 3

(21) Differences between Embodiment 3 and Embodiment 2 may include: on the basis of Embodiment 2, doping concentration of the second P-type semiconductor layer adjacent to the transient layer is lowered to fabricate a segmented doping P-type semiconductor layer. As shown in FIG. 3, grow a P-type semiconductor layer over the quantum well light-emitting layer 230, preferably made of Al.sub.xIn.sub.(1-x)P. Set growth temperature to 670 C. and reaction chamber pressure to 60 Torr. Doping material is Mg. During growth of the first P-type semiconductor layer 241 adjacent to the quantum well light-emitting layer, input Cp.sub.2Mg, and continue inputting for 10 min when flow setting remains unchanged. The doping concentration is 1.010.sup.18 cm.sup.3 and growth thickness is about 0.5 m. Next, during growth of the second P-type semiconductor layer 242 adjacent to the transient layer, Mg flow is decreased 20% with 1 min gradient method; then, keep stable growth for 3 min; maintain doping concentration at 0.810.sup.18 cm.sup.3. The thickness is about 0.15 m, which is 30% of thickness of the first P-type semiconductor layer. A segmented doping P-type semiconductor layer structure is therefore fabricated.

(22) In this new-type AlGaInP structure LED, after fabrication of the P-type electrode 270 and the N-type electrode 280, a small-size chip of 5.8 mil5.8 mil is used for evaluation. Under 100 mA and 50 C., long-term aging light attenuation value can be controlled within 3%. This indicates that the resistance to aging caused by high current can be effectively improved by lowering doping concentration of the P-type semiconductor layer adjacent to the transient layer.

Embodiment 4

(23) Differences between Embodiment 4 and Embodiment 3 may include: extend growth time of the first P-type semiconductor layer adjacent to the quantum well, and shorten growth time of the second P-type semiconductor layer adjacent to the transient layer to optimize thickness ratio. Reduce the doping flow set value of the second P-type semiconductor layer to about 0.510.sup.18 cm.sup.3, which is 50% of that of the first P-type semiconductor layer to optimize doping ratio.

(24) The P-type semiconductor is over the quantum well light-emitting layer.

(25) Set growth temperature to 670 C., and reaction chamber pressure to 60 Torr. The doping material is Mg. During growth of the first P-type semiconductor layer, input Cp.sub.2Mg, and continue inputting for 12 min when flow setting remains unchanged. The doping concentration is 1.010.sup.18 cm.sup.3 and growth thickness is about 0.6 m. During growth of the second P-type semiconductor layer, reduce Mg flow to 50% with 1 min gradient method, and keep stable growth for 1.8 min. Maintain doping concentration at 0.510.sup.18 cm.sup.3. The thickness is about 0.09 m, which is 15% of that of the first P-type semiconductor layer. A segmented P-type semiconductor structure with preferred performance is therefore fabricated.

(26) On the basis of Embodiment 3, Embodiment 4 further improves the segmented P-type doping layer structure with further optimized doping concentration ratio and thickness ratio. In Embodiment 4, doping of the second P-type semiconductor layer adjacent to the transient layer is further lowered to optimize anti-aging performance. Moreover, voltage VFavg is kept stable by increasing thickness of the first P-type semiconductor layer and reducing thickness of the second P-type semiconductor layer. Through this optimization scheme of thickness ratio and doping ratio, the resistance to aging caused by high current can be further improved to improve LED reliability.

(27) In this new-type AlGaInP structure LED, after fabrication of the P-type electrode 270 and the N-type electrode 280, a small-size chip of 5.8 mil5.8 mil is used for evaluation. Under 100 mA and 50 C., long-term aging light attenuation value can be controlled within 1.5% under 100 mA and 50 C.

(28) Although specific embodiments have been described above in detail, the description is merely for purposes of illustration. It should be appreciated, therefore, that many aspects described above are not intended as required or essential elements unless explicitly stated otherwise. Various modifications of, and equivalent acts corresponding to, the disclosed aspects of the exemplary embodiments, in addition to those described above, can be made by a person of ordinary skill in the art, having the benefit of the present disclosure, without departing from the spirit and scope of the disclosure defined in the following claims, the scope of which is to be accorded the broadest interpretation so as to encompass such modifications and equivalent structures.