Deep ultraviolet light-emitting device and method of manufacturing same

1. A deep ultraviolet light-emitting device comprising on a substrate in order: an n-type semiconductor layer, a light-emitting layer, a p-type electron block layer, and a p-type contact layer, wherein

the p-type contact layer comprises a superlattice structure having an alternating stack of: a first layer made of Al x Ga 1-x N having an Al composition ratio x higher than an Al composition ratio w 0 of a layer configured to emit deep ultraviolet light in the light-emitting layer; and a second layer made of Al y Ga 1-y N having an Al composition ratio y lower than the Al composition ratio x, and

the Al composition ratio w 0 , the Al composition ratio x, the Al composition ratio y, and a thickness average Al composition ratio z of the p-type contact layer satisfy the following formulas [1] and [2]:

0.030< z−w 0 <0.20  [1]

0.050≤ x−y≤ 0.47  [2].

2. The deep ultraviolet light-emitting device of claim 1 , wherein a terminal layer closer to the p-type electron block layer in a thickness direction of the p-type contact layer is the first layer.

3. The deep ultraviolet light-emitting device of claim 1 , wherein a terminal layer farther from the p-type electron blocking layer in a thickness direction of the p-type contact layer is the second layer.

4. The deep ultraviolet light-emitting device of claim 1 , wherein the light-emitting layer has a quantum-well structure formed of an alternating stack of a well layer and a barrier layer.

5. The deep ultraviolet light-emitting device of claim 4 , further comprising a guide layer having an Al composition ratio higher than any of Al composition ratios of the barrier layer and the p-type electron block layer, the guide layer being disposed between the well layer closest to the p-type electron block layer in the light-emitting layer and the p-type electron block layer.

6. The deep ultraviolet light-emitting device of claim 5 , wherein the guide layer is made of AIN.

7. The deep ultraviolet light-emitting device of claim 1 , wherein the Al composition ratio w 0 is 0.25 or more 0.60 or less.

8. The deep ultraviolet light-emitting device of claim 1 , wherein the p-type contact layer has a high concentration area having a Mg concentration of 3×10 20 atoms/cm 3 or more on a surface side on which a p-side electrode is to be formed, the surface side facing away from the p-type electron block layer.

9. The deep ultraviolet light-emitting device of claim 1 , wherein the p-type contact layer has a Si-doped area having a Si concentration of 5×10 16 atoms/cm 3 or more and 1×10 20 atoms/cm 3 or less on a surface side on which a p-side electrode is to be formed, the surface side facing away from the p-type electron block layer.

10. A method of manufacturing a deep ultraviolet light-emitting device, comprising the steps of:

forming an n-type semiconductor layer on a substrate;

forming a light-emitting layer on the n-type semiconductor layer;

forming a p-type electron block layer on the light-emitting layer; and

forming a p-type contact layer on the p-type electron block layer, wherein

in forming the p-type contact layer, a first step of forming a first layer made of Al x Ga 1-x N having an Al composition ratio x higher than an Al composition ratio w 0 of a layer configured to emit deep ultraviolet light in the light-emitting layer, and a second step of forming a second layer made of Al y Ga 1-y N having an Al composition ratio y lower than the Al composition ratio x are alternately repeated to form the p-type contact layer having a superlattice structure, and

the Al composition ratio w 0 , the Al composition ratio x, the Al composition ratio y, and a thickness average Al composition ratio z of the p-type contact layer satisfy the following formulas [1] and [2]:

0.030< z−w 0 <0.20  [1]

0.050≤ x−y≤ 0.47  [2].