Method of growing a high quality iii-v compound layer on a silicon substrate

Abstract

The present disclosure involves a method of fabricating a semiconductor device. A surface of a silicon wafer is cleaned. A first buffer layer is then epitaxially grown on the silicon wafer. The first buffer layer contains an aluminum nitride (AlN) material. A second buffer layer is then epitaxially grown on the first buffer layer. The second buffer layer includes a plurality of aluminum gallium nitride (Al x Ga 1−x N) sub-layers. Each of the sub-layers has a respective value for x that is between 0 and 1. A value of x for each sub-layer is a function of its position within the second buffer layer. A first gallium nitride (GaN) layer is epitaxially grown over the second buffer layer. A third buffer layer is then epitaxially grown over the first GaN layer. A second GaN layer is then epitaxially grown over the third buffer layer.

What is claimed is: 
     
         1 . A semiconductor apparatus, comprising:
 a substrate;   a first buffer layer disposed over the substrate, wherein the first buffer layer contains a III-V compound that includes a first group III element and a group V element;   a second buffer layer disposed over the first buffer layer; and   a first III-V compound bulk layer disposed over the second buffer layer;   wherein:
 the second buffer layer includes a plurality of sub-layers each contains the first group III element, the group V element, and a second group III element; 
 a content of the first group III element decreases for each sub-layer that is located further away from the first buffer layer; and 
 a first sub-layer that is in the plurality of sub-layers and disposed closest to the first buffer layer has a smallest thickness less than that of each of the rest of the sub-layers. 
   
     
     
         2 . The semiconductor apparatus of  claim 1 , wherein the first group III element is aluminum. 
     
     
         3 . The semiconductor apparatus of  claim 1 , wherein:
 the first buffer layer contains aluminum nitride (AlN);   the sub-layers of the second buffer layer each contains aluminum gallium nitride (Al x Ga 1−x N), wherein 0<x<1; and   the first III-V compound bulk layer contains gallium nitride (GaN).   
     
     
         4 . The semiconductor apparatus of  claim 1 , wherein the first buffer layer has a thickness less than about 100 nanometers (nm). 
     
     
         5 . The semiconductor apparatus of  claim 1 , wherein the first sub-layer has a thickness less than about 100 nm, while the rest of the sub-layers each has a thickness greater than about 100 nm. 
     
     
         6 . The semiconductor apparatus of  claim 1 , wherein the first and second buffer layers have different thicknesses that are associated with their respective concentrations of the first group III element. 
     
     
         7 . The semiconductor apparatus of  claim 1 , further comprising:
 a third buffer layer disposed over the first III-V compound bulk layer;   a fourth buffer layer disposed between the second buffer layer and the first III-V compound bulk layer, wherein the fourth buffer layer is thinner than each of the first buffer layer, the first III-V compound bulk layer, and each of the sub-layers of the second buffer layer, and wherein the fourth buffer layer has a lower aluminum content than that of each of the sub-layers of the second buffer layer; and   a second III-V compound bulk layer disposed over the third buffer layer, wherein the second III-V compound bulk layer is substantially thicker than the first III-V compound bulk layer.   
     
     
         8 . The semiconductor apparatus of  claim 7 , wherein the second III-V compound bulk layer is at least three times thicker than the first III-V compound bulk layer. 
     
     
         9 . The semiconductor apparatus of  claim 7 , wherein:
 the third buffer layer contains AlN or Al x Ga 1−x N/GaN; and   the first III-V compound bulk layer and the second III-V compound bulk layer each contains GaN.   
     
     
         10 . The semiconductor apparatus of  claim 1 , wherein the substrate is a silicon substrate. 
     
     
         11 . The semiconductor apparatus of  claim 1 , wherein the semiconductor apparatus comprises a light-emitting diode (LED), a radio frequency (RF) device, a high electron mobility transistor (HEMT) device, or a high power semiconductor device. 
     
     
         12 . A semiconductor apparatus, comprising:
 a silicon substrate;   an aluminum nitride (AlN) buffer layer located on the silicon substrate;   a composite buffer layer located on the AlN buffer layer, the composite buffer layer including a plurality of aluminum gallium nitride (Al x Ga 1− N) sub-layers in a stacked arrangement such that a top surface of a lower sub-layer directly contacts a bottom surface of an upper sub-layer, wherein x of a given sub-layer is smaller than x of an adjacent below sub-layer and 0<x<1; wherein a first sub-layer that is in the plurality of sub-layers and disposed closest to the AlN buffer layer has a smallest thickness less than that of each of the rest of the sub-layers; and   a first III-V compound bulk layer located over the composite buffer layer.   
     
     
         13 . The semiconductor apparatus of  claim 12 , wherein the first III-V compound bulk layer contains gallium nitride (GaN). 
     
     
         14 . The semiconductor apparatus of  claim 12 , wherein the first sub-layer has a thickness less than about 100 nm, and the rest of the sub-layers each have a thickness greater than about 100 nm. 
     
     
         15 . The semiconductor apparatus of  claim 12 , wherein the AlN buffer layer has a thickness less than about 100 nanometers (nm). 
     
     
         16 . The semiconductor apparatus of  claim 12 , further comprising:
 an insertion layer disposed on the first III-V bulk layer; and   a second III-V compound bulk layer located on the insertion layer, wherein the second III-V compound bulk layer is substantially thicker than the first III-V compound bulk layer, wherein the first and second III-V compound bulk layers contain a material that is other than aluminum gallium nitride,   wherein the plurality of the Al x Ga 1−x N sub-layers have different thicknesses that are associated with their respective Al concentration.   
     
     
         17 . The semiconductor apparatus of  claim 16 , wherein:
 the first III-V compound bulk layer and the second III-V compound bulk layer each contains gallium nitride (GaN); and   the insertion layer contains AN or Al x Ga 1−x N/GaN.   
     
     
         18 . The semiconductor apparatus of  claim 12 , wherein the semiconductor apparatus comprises a light-emitting diode (LED), a radio frequency (RF) device, a high electron mobility transistor (HEMT) device, or a high power semiconductor device. 
     
     
         19 . The semiconductor apparatus of  claim 16 , wherein the second III-V compound bulk layer is at least three times thicker than the first III-V compound bulk layer.