Method for fabricating nitride-based semiconductor device having electrode on
View Patent ↗A nitride-based semiconductor light-emitting device 100 includes a GaN substrate 10 , of which the principal surface is an m-plane 12 , a semiconductor multilayer structure 20 that has been formed on the m-plane 12 of the GaN-based substrate 10 , and an electrode 30 arranged on the semiconductor multilayer structure 20 . The electrode 30 includes an Mg alloy layer 32 which is formed of Mg and a metal selected from a group consisting of Pt, Mo, and Pd. The Mg alloy layer 32 is in contact with a surface of a p-type semiconductor region of the semiconductor multilayer structure 20.
1. A method for fabricating a nitride-based semiconductor device, comprising the steps of:
(a) providing a substrate;
(b) forming on the substrate a nitride-based semiconductor multilayer structure including a p-type GaN-based semiconductor region, a surface of the p-type GaN-based semiconductor region being an m-plane; and
(c) forming an electrode on the surface of the p-type GaN-based semiconductor region of the semiconductor multilayer structure,
wherein step (c) includes forming an Mg alloy layer on the surface of the p-type Gan-based semiconductor region, the Mg alloy layer being made of Mg and a metal selected from a group consisting of Pt, Mo, and Pd,
wherein a heat treatment is performed to anneal the electrode at a temperature of 500°C. to 700°C., and
wherein a contact resistance of the electrode arranged on the m-plane and annealed at a temperature of 500°C. to 700°C. is less than 1.0×10 −02 Ω cm 2 , and is lower than a contact resistance when the electrode is arranged on a c-plane of the same p-type semiconductor region and annealed at a temperature of 500°C. to 700°C.
2. The method of claim 1 , wherein the heat treatment is performed at a temperature of 550° C. to 650° C.
3. The method of claim 1 , wherein the p-type GaN-based semiconductor region is made of an Al x In y Ga z N semiconductor (where x+y+z=1, x≧0, y≧0, and z>0).
4. The method of claim 3 , wherein the step of forming the Mg alloy layer includes
forming an Mg layer on the surface of the p-type GaN-based semiconductor region,
forming on the Mg layer a conductive layer selected from a group consisting of Pt, Mo, and Pd, and
performing the heat treatment to alloy the Mg layer and at least part of the conductive layer.
5. The method of claim 4 , wherein the step of forming the Mg layer includes irradiating Mg with pulses of an electron beam such that Mg is deposited onto the surface of the p-type GaN-based semiconductor region.
6. The method of claim 4 , wherein the Mg layer is deposited on the semiconductor multilayer structure so as to have a thickness of 0.1 nm to 5 nm.
7. The method of claim 3 , further comprising removing the substrate after step (b).
8. The method of claim 3 , wherein the step of forming the Mg alloy layer includes
depositing a mixture or compound of Mg and a metal selected from a group consisting of Pt, Mo, and Pd onto the surface of the p-type GaN-based semiconductor region by means of evaporation, and
performing a heat treatment.