HIGH EFFICIENCY ULTRAVIOLET LIGHT EMITTING DIODE WITH BAND STRUCTURE POTENTIAL FLUCTUATIONS

• US 20160211411A1
• Filed: 04/08/2015
• Published: 07/21/2016
• Est. Priority Date: 04/30/2010
• Status: Active Grant

• Current Assignee: Trustees of Boston University
• Original Assignee: Trustees of Boston University
• Inventors: Liao, Yitao, Moustakas, Theodore D.
• Granted Patent: US 10,535,801 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02573 Conductivity type
• CPC Class Codes: H01L 21/0259 Microstructure
• CPC Class Codes: H01L 21/02625 using melted materials
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/025 Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A method of growing an AlGaN semiconductor material utilizes an excess of Ga above the stoichiometric amount typically used. The excess Ga results in the formation of band structure potential fluctuations that improve the efficiency of radiative recombination and increase light generation of optoelectronic devices, in particular ultraviolet light emitting diodes, made using the method. Several improvements in UV LED design and performance are also provided for use together with the excess Ga growth method. Devices made with the method can be used for water purification, surface sterilization, communications, and data storage and retrieval.

Claims

1. A device comprising:

an active layer disposed between an n-type region and a p-type region, wherein the active layer emits ultraviolet radiation in the wavelength range between 210 nm and 360 nm;

a first layer having a smaller band gap than the active layer; and

a second layer disposed between the first layer and the active layer, wherein the second layer has a band gap larger than both the active layer and the first layer.

2. The device of claim 1 wherein the first layer is doped with an n-type dopant and is disposed in the n-type region.

3. The device of claim 1 wherein the second layer is undoped.

4. The device of claim 1 wherein electrons are injected from the first layer into the active layer by tunneling through the second layer.

5. The device of claim 1 wherein the first layer is disposed in the n-type region, the n-type region further comprising a third layer have a larger band gap than both the active layer and the first layer.

6. The device of claim 5 wherein the first layer is disposed between the second layer and the third layer.

7. The device of claim 1 wherein the active layer, first layer, and second layer are AlGaN.

8. The device of claim 1 wherein:

the active layer is a quantum well layer;

the second layer is a first barrier layer disposed between the active layer and the n-type region; and

a second barrier layer is disposed between the active layer and the p-type region.

9. The device of claim 1 wherein the active layer has an average aluminum concentration and an average gallium concentration across a total lateral extent of the active layer, and a reduced aluminum concentration and a greater gallium concentration as compared to the average aluminum concentration and the average gallium concentration in a localized region, the localized region having a lateral extent that is less than the total lateral extent of the active layer.

10. The device of claim 1 wherein the active layer is non-faceted.

11. The device of claim 1 wherein the active layer emits radiation having a peak wavelength less than 350 nm.

12. A device comprising:

an active layer disposed between an n-type region and a p-type region;

a barrier layer disposed between the active layer and the n-type region, wherein electrons are injected from the n-type region into the active layer by tunneling through the barrier layer, and wherein the barrier layer is undoped.

13. The device of claim 12 wherein the n-type region comprises a first layer having a band gap smaller than the active layer and a second layer having a band gap larger than the active layer, wherein the first layer is disposed between the barrier layer and the second layer.

14. The device of claim 13 wherein the active layer, the barrier layer, the first layer, and the second layer are AlGaN.

15. The device of claim 12 wherein the n-type region comprises a first layer having a band gap greater than the barrier layer and a second layer having a bandgap less than the barrier layer, wherein the second layer is disposed between the barrier layer and the first layer.

16. The device of claim 12 wherein the active layer emits ultraviolet radiation.

17. A device comprising:

an active layer disposed between an n-type region and a p-type region, wherein the active layer emits radiation in a range of 230 nm-350 nm;

a barrier layer disposed between the active layer and the n-type region, wherein electrons are injected from the n-type region into the active layer by tunneling through the barrier layer.

18. The device of claim 17 wherein the n-type region comprises a first layer having a band gap smaller than the active layer and a second layer having a band gap larger than the active layer, wherein the first layer is disposed between the barrier layer and the second layer.

19. The device of claim 18 wherein the active layer, the barrier layer, the first layer, and the second layer are AlGaN.

20. The device of claim 17 wherein the barrier layer is undoped.