Transparent positive electrode
An object of the present invention is to provide a positive electrode having high transparency, low contact resistance and excellent current diffusibility and not requiring electron beam irradiation, high-temperature annealing or heat treatment, for alloying, in an oxygen atmosphere. The inventive transparent positive electrode for gallium nitride-based compound semiconductor light-emitting devices comprises a contact metal layer in contact with a p-type semiconductor layer, a current diffusing layer on the contact metal layer, the current diffusing layer having an electrical conductivity larger than that of the contact metal layer, and a bonding pad layer on the current diffusing layer.
1. A gallium nitride-based compound semiconductor light-emitting device comprising a transparent positive electrode having a contact metal layer in contact with a p-type semiconductor layer, a current diffusing layer on the contact metal layer, the current diffusing layer having an electrical conductivity larger than that of the contact metal layer, and a bonding pad layer on the current diffusing layer, wherein the thickness of the contact metal layer is from 0.1 to 7.5 nm.
2. The gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the contact metal layer is a platinum group metal or an alloy containing a platinum group metal.
3. The gallium nitride-based compound semiconductor light-emitting device according to claim 2 , wherein the contact metal layer is platinum.
4. The gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the thickness of the contact metal layer is from 0.1 to 5 nm.
5. The gallium nitride-based compound semiconductor light-emitting device according to claim 4 , wherein the thickness of the contact metal layer is from 0.5 to 2.5 nm.
6. The gallium nitride-based compound semiconductor light-emitting device according to claim 1 wherein the current diffusing layer is a metal selected from the group consisting of gold, silver and copper, or an alloy containing at least one member of gold, silver and copper.
7. The gallium nitride-based compound semiconductor light-emitting device according to claim 6 , wherein the current diffusing layer is gold.
8. The gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the thickness of the current diffusing layer is from 1 to 20 nm.
9. The gallium nitride-based compound semiconductor light-emitting device according to claim 8 , wherein the thickness of the current diffusing layer is from 1 to 10 nm.
10. The gallium nitride-based compound semiconductor light-emitting device according to claim 9 , wherein the thickness of the current diffusing layer is from 3 to 6 nm.