Carbon doping semiconductor devices

Abstract

A method of fabricating a semiconductor device can include forming a III-N semiconductor layer in a reactor and injecting a hydrocarbon precursor into the reactor, thereby carbon doping the III-N semiconductor layer and causing the III-N semiconductor layer to be insulating or semi-insulating. A semiconductor device can include a substrate and a carbon doped insulating or semi-insulating III-N semiconductor layer on the substrate. The carbon doping density in the III-N semiconductor layer is greater than 5×10 18 cm −3 and the dislocation density in the III-N semiconductor layer is less than 2×10 9 cm −2 .

What is claimed is: 
     
         1 . A method of fabricating a semiconductor material structure, the method comprising:
 forming a III-N semiconductor layer on a substrate in a reactor, the forming of the III-N semiconductor layer comprising simultaneously injecting into the reactor a first precursor, a second precursor different from the first precursor, and a group-V precursor, wherein the first precursor is a group-III precursor and the second precursor is a hydrocarbon precursor, and the injecting of the hydrocarbon precursor causes the III-N semiconductor layer to be carbon doped.   
     
     
         2 . The method of  claim 1 , wherein the hydrocarbon precursor comprises molecules having a chemical formula (C x H y ), where x and y are integers greater than or equal to 1, and the group-III precursor comprises a metalorganic precursor. 
     
     
         3 . The method of  claim 1 , wherein forming the III-N semiconductor layer on the substrate comprises forming the III-N semiconductor layer as a III-N buffer layer over a III-N nucleation layer over a silicon substrate. 
     
     
         4 . The method of  claim 3 , further comprising forming a III-N channel layer over the III-N buffer layer and forming a III-N barrier layer over the III-N channel layer, thereby forming a two-dimensional electron gas (2DEG) active channel adjacent to an interface between the channel layer and the barrier layer. 
     
     
         5 . The method of  claim 4 , wherein the barrier layer comprises AlGaN, the channel layer comprises undoped or unintentionally doped (UID) GaN, and the buffer layer comprises AlGaN or GaN or both. 
     
     
         6 . The method of  claim 1 , wherein the hydrocarbon precursor comprises propane or methane or both. 
     
     
         7 . The method of  claim 1 , wherein causing the III-N semiconductor layer to be carbon doped results in the III-N semiconductor layer having a carbon concentration greater than ×10 18  cm 3 . 
     
     
         8 . The method of  claim 1 , wherein forming the III-N semiconductor layer on the substrate comprises forming the III-N semiconductor layer by metal organic chemical vapor deposition (MOCVD). 
     
     
         9 . A method of fabricating a semiconductor material structure, the method comprising:
 forming a III-N semiconductor layer on a substrate in a reactor, the forming of the III-N semiconductor layer comprising simultaneously injecting into the reactor a group-III precursor selected from the group consisting of TMGa and TMAl, a group-V precursor, and a hydrocarbon precursor comprising molecules having a chemical formula (C x H y ), where x and y are integers greater than or equal to 1; wherein the injecting of the hydrocarbon precursor causes the III-N semiconductor layer to be carbon doped.   
     
     
         10 . The method of  claim 9 , wherein the injecting of the group-III precursor into the reactor comprises injecting the group-III precursor at a group-III precursor molar flow rate, and the injecting of the hydrocarbon precursor into the reactor comprises injecting the hydrocarbon precursor at a hydrocarbon precursor molar flow rate different from the group-III precursor molar flow rate. 
     
     
         11 . The method of  claim 10 , wherein the hydrocarbon precursor molar flow rate is at least 0.02 times the group-III precursor molar flow rate. 
     
     
         12 . The method of  claim 11 , wherein the hydrocarbon precursor molar flow rate is greater than the group-III precursor molar flow rate. 
     
     
         13 . The method of  claim 9 , wherein the hydrocarbon precursor comprises propane or methane or both. 
     
     
         14 . The method of  claim 9 , wherein forming the III-N semiconductor layer on the substrate comprises forming the III-N semiconductor layer by metal organic chemical vapor deposition (MOCVD). 
     
     
         15 . A method of fabricating a semiconductor material structure, the method comprising:
 forming a first III-N semiconductor layer in a reactor, the first III-N semiconductor layer being carbon doped; and   forming a second III-N semiconductor layer on the first III-N semiconductor layer in the reactor; wherein   the forming of the first III-N semiconductor layer comprises injecting into the reactor a group-III precursor, a group-V precursor, and a hydrocarbon precursor, and the forming of the second III-N semiconductor layer comprises injecting into the reactor the group-III precursor and the group-V precursor but not the hydrocarbon precursor.   
     
     
         16 . The method of  claim 15 , wherein the second III-N semiconductor layer is undoped or unintentionally doped. 
     
     
         17 . The method of  claim 15 , wherein the group-III precursor comprises TMGa or TMAl, the group-V precursor comprises ammonia, and the hydrocarbon precursor comprises molecules having a chemical formula (C x H y ), where x and y are integers greater than or equal to 1. 
     
     
         18 . The method of  claim 15 , wherein the carbon concentration in the first III-N semiconductor layer is in excess of 1×10 17  cm −3 . 
     
     
         19 . The method of  claim 15 , wherein the hydrocarbon precursor comprises propane or methane or both. 
     
     
         20 . The method of  claim 15 , wherein forming the III-N semiconductor layer on the substrate comprises forming the III-N semiconductor layer by metal organic chemical vapor deposition (MOCVD).