Method for treating surface of semiconductor layer, semiconductor substrate, method for making epitaxial substrate

Abstract

A surface treatment method for a semiconductor layer includes growing a first layer on a substrate in a growth reactor, the first layer consisting of one of gallium nitride, aluminum gallium nitride and indium aluminium nitride; growing a second layer of gallium nitride on a surface of the first layer, the gallium nitride of the second GaN layer having a composition ratio of gallium to nitrogen larger than 2; taking the substrate out of the growth reactor after growing the second layer; and removing the second layer after taking the substrate out of the growth reactor.

What is claimed is: 
     
         1 . A method for treating a surface of a semiconductor layer, the method comprising the steps of:
 growing a first layer on a substrate in a growth reactor, the first layer consisting of one of gallium nitride, aluminum gallium nitride and indium aluminium nitride;   growing a second layer of gallium nitride on a surface of the first layer, the gallium nitride of the second GaN layer having a composition ratio of gallium to nitrogen larger than 2;   taking the substrate out of the growth reactor after growing the second layer; and   removing the second layer after taking the substrate out of the growth reactor.   
     
     
         2 . The method according to  claim 1 , wherein growing a second layer on a surface of the first layer includes a step of forming the second layer on the first layer using an MOCVD reactor at a substrate temperature equal to or lower than 800 degrees Celsius. 
     
     
         3 . The method according to  claim 1 , wherein, removing the second layer includes removing the second layer using mixed liquid including sulfur acid and hydrogen peroxide. 
     
     
         4 . The method according to  claim 1 , wherein the growth reactor includes an introducing port for introducing gas above the substrate. 
     
     
         5 . The method according to  claim 1 , wherein an accreting object are formed on the second layer after growing the second layer, and the accreting object is removed in the step of removing the second layer. 
     
     
         6 . The method according to  claim 1 , wherein the first layer and the second layer are continuously grown in the growth reactor. 
     
     
         7 . A semiconductor substrate comprising:
 a first layer consisting of one of gallium nitride, aluminum gallium nitride and indium aluminium nitride; and   a second layer of gallium nitride having a composition ratio of gallium to nitrogen larger than 2, the second layer being provided on the first layer.   
     
     
         8 . The semiconductor substrate according to  claim 7 , further comprising particles containing gallium, the particles being provided on the second layer. 
     
     
         9 . The semiconductor substrate according to  claim 7 , wherein a film thickness of the second layer is equal to or larger than 100 nm. 
     
     
         10 . The semiconductor substrate according to  claim 7 , wherein the second layer is formed to be in contact with the first layer. 
     
     
         11 . A method for making an epitaxial substrate, comprising the steps of:
 growing a first layer on a substrate in a growth reactor, the first layer consisting of one of gallium nitride, aluminum gallium nitride and indium aluminium nitride;   growing a second layer of gallium nitride compound on the first layer in the growth reactor, the first layer being in contact with the second layer, and the gallium nitride compound having a composition ratio of gallium to nitrogen larger than 2;   taking the substrate out of the growth reactor after growing the second layer; and   etching the second layer to expose the first layer after taking the substrate from the growth reactor.   
     
     
         12 . The method according to  claim 11 , wherein growing a second layer on a surface of the first layer includes a step of forming the second layer on the first layer using an MOCVD reactor at a substrate temperature equal to or lower than 800 degrees Celsius. 
     
     
         13 . The method according to  claim 11 , wherein, removing the second layer includes removing the second layer using mixed liquid including sulfuric acid and hydrogen peroxide. 
     
     
         14 . The method according to  claim 11 , wherein the growth reactor includes an introducing port for introducing gas above the substrate. 
     
     
         15 . The method according to  claim 11 , wherein an accreting object are formed on the second layer after growing the second layer, and the accreting object is etched in the step of etching the second layer.