Nitride-based semiconductor device and method for fabricating the same

Abstract

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 layer 32 , which contacts with the surface of a p-type semiconductor region in the semiconductor multilayer structure 20.

1 . A nitride-based semiconductor device comprising:
 a nitride-based semiconductor multilayer structure including a p-type semiconductor region, a surface of the p-type semiconductor region being an m-plane; and   an electrode that is arranged on the p-type semiconductor region,   wherein the p-type 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), and   wherein the electrode comprises an Mg-containing layer that is in contact with the surface of the p-type semiconductor region.   
     
     
         2 . The nitride-based semiconductor device of  claim 31 , wherein the electrode comprises the Mg-containing layer and a metal layer that has been stacked on the Mg-containing layer, and
 wherein the metal layer is made of at least one metal selected from the group consisting of Pt, Mo and Pd.   
     
     
         3 . The nitride-based semiconductor device of  claim 2 , wherein a metal alloy layer, including Mg and the at least one metal selected from the group consisting of Pt, Mo and Pd, is sandwiched between the Mg-containing layer and the metal layer. 
     
     
         4 . The nitride-based semiconductor device of  claim 31 , wherein the electrode comprises the Mg-containing layer and a metal alloy layer that has been formed on the Mg-containing layer, and
 wherein the metal alloy layer is made of an alloy of Mg and at least one metal selected from the group consisting of Pt, Mo and Pd.   
     
     
         5 . The nitride-based semiconductor device of  claim 3 , wherein the Mg-containing layer is made up of a film that is present on the surface of the p-type semiconductor region. 
     
     
         6 . The nitride-based semiconductor device of  claim 3 , wherein the Mg-containing layer is made up of islands of Mg portions that are present on the surface of the p-type semiconductor region. 
     
     
         7 . The nitride-based semiconductor device of  claim 31 , wherein the semiconductor multilayer structure has an active layer including an Al a In b Ga c N layer (where a+b+c=1, a≧0, b≧0 and c≧0) and emitting light. 
     
     
         8 . The nitride-based semiconductor device of  claim 31 , wherein the Mg-containing layer has a thickness of 2 nm to 45 nm. 
     
     
         9 . The nitride-based semiconductor device of  claim 8 , wherein the Mg-containing layer has a thickness of 2 nm to 15 nm. 
     
     
         10 . The nitride-based semiconductor device of  claim 2 , wherein the thickness of the Mg-containing layer is equal to or smaller than that of the metal layer. 
     
     
         11 . The nitride-based semiconductor device of  claim 31 , wherein the concentration of Ga in the Mg-containing layer is higher than that of nitrogen in the same Mg-containing layer. 
     
     
         12 . The nitride-based semiconductor device of  claim 11 , wherein the concentration of Ga is ten times or more as high as that of nitrogen. 
     
     
         13 . The nitride-based semiconductor device of  claim 31 , further comprising a semiconductor substrate that supports the semiconductor multilayer structure. 
     
     
         14 . The nitride-based semiconductor device of  claim 1 , wherein the p-type semiconductor region is made of GaN. 
     
     
         15 . A light source comprising
 a nitride-based semiconductor light-emitting device, and   a wavelength converter including a phosphor that changes the wavelength of the light that has been emitted from the nitride-based semiconductor light-emitting device,   wherein the nitride-based semiconductor light-emitting device includes:   a nitride-based semiconductor multilayer structure including a p-type semiconductor region, of which the surface is an m-plane; and   an electrode that is arranged on the p-type semiconductor region,   wherein the p-type 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), and   wherein the electrode comprises an Mg-containing layer that is in contact with the surface of the p-type semiconductor region.   
     
     
         16 . The light source of  claim 15 , wherein the p-type semiconductor region is made of GaN. 
     
     
         17 . A method for fabricating a nitride-based semiconductor device, the method comprising the steps of:
 (a) providing a substrate;   (b) forming a nitride-based semiconductor multilayer structure, including a p-type semiconductor region, on the substrate, the p-type semiconductor region having an m-plane as its surface and being made of an Al x In y Ga z N semiconductor (where x+y+z=1, x≧0, y≧0 and z≧0); and   (c) forming an electrode on the surface of the p-type semiconductor region of the semiconductor multilayer structure,   wherein the step (c) includes the step of forming an Mg layer on the surface of the p-type semiconductor region.   
     
     
         18 . The method of  claim 33 , wherein the step (c) includes the step of forming a metal layer, which is made of at least one metal selected from the group consisting of Pt, Mo and Pd, after the Mg layer has been formed. 
     
     
         19 . The method of  claim 18 , wherein the step (c) includes the step of subjecting the Mg layer to a heat treatment after the metal layer has been formed. 
     
     
         20 . The method of  claim 19 , wherein the heat treatment is carried out at a temperature of 500° C. to 700° C. 
     
     
         21 . The method of  claim 20 , wherein the heat treatment is carried out at a temperature of 550° C. to 650° C. 
     
     
         22 . The method of  claim 33 , wherein the step of forming the Mg layer includes depositing Mg by evaporation onto the surface of the p-type semiconductor region by irradiating the surface with pulses of an electron beam. 
     
     
         23 . The method of  claim 19 , comprising the step of adjusting the thickness of the Mg layer to the range of 2 nm to 45 nm after the heat treatment. 
     
     
         24 . The method of  claim 33 , wherein the step (b) includes the step of forming a layer of an Al x In y Ga z N semiconductor (where x+y+z=1, x≧0, y≧0 and z≧0). 
     
     
         25 . The method of one of  claim 33 , comprising the step of removing the substrate after the step (b) has been performed. 
     
     
         26 . The method of  claim 33 , wherein the concentration of Ga in the Mg layer is higher than that of nitrogen in the same Mg layer. 
     
     
         27 . The method of  claim 33 , wherein the concentration of Ga is ten times or more as high as that of nitrogen. 
     
     
         28 . The method of  claim 17 , wherein the p-type semiconductor region is made of GaN. 
     
     
         29 . A method of forming an Mg thin film to be an electrode for a semiconductor device, comprising the steps of: forming an Mg thin film on a surface of a p-type GaN-based semiconductor layer by irradiating Mg with pulses of an electron beam and evaporating Mg. 
     
     
         30 . The method of  claim 29 , wherein the Mg thin film is formed without heating a supporting member on which the Mg thin film is going to be formed. 
     
     
         31 . The nitride-based semiconductor device of  claim 1 , wherein a p-type semiconductor region is made of GaN based semiconductor. 
     
     
         32 . The light source of  claim 15 , wherein the p-type semiconductor region is made of GaN based semiconductor. 
     
     
         33 . The method of  claim 17 , wherein the p-type semiconductor region is made of GaN based semiconductor. 
     
     
         34 . A nitride-based semiconductor device comprising:
 a nitride-based semiconductor multilayer structure including a p-type semiconductor region, a surface of the p-type semiconductor region being an m-plane; and   an electrode that is arranged on the p-type semiconductor region,   wherein the p-type 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),   wherein the electrode comprises an Mg-containing layer that is in contact with the surface of the p-type semiconductor region, and a metal alloy layer that has been formed on the Mg-containing layer, and, and   wherein the metal alloy layer is made of an alloy of Mg and at least one metal selected from the group consisting of Pt, Mo and Pd.   
     
     
         35 . The nitride-based semiconductor of  claim 34 , wherein the p-type semiconductor region is made of GaN based semiconductor.