Semiconductor structure having a Si substrate heterointegrated with GaN and method for fabricating the same
A semiconductor structure having a Si substrate heterointegrated with GaN and a method for fabricating the same is disclosed. The method uses a (100) silicon substrate to fabricate a hundred nanometer scale hole and uses wet etching to etch the silicon substrate, thereby exposing the (111) crystal surface of the silicon substrate. The (111) crystal surface is used as a nucleating crystal surface of an AlN buffer layer and GaN. When GaN is grown, silane is reacted with GaN to adjust the concentration of doping silicon atoms into GaN, thereby forming a semiconductor structure having a Si substrate heterointegrated with GaN.
1. A method for fabricating a semiconductor structure having a Si substrate heterointegrated with GaN comprising:
providing a silicon substrate having a main surface, which has a (100) crystal surface and growing an oxide layer on the main surface;
patterning the oxide layer to serve as a hard mask and using reactive-ion etching (RIE) to etch the silicon substrate, thereby forming a hundred nanometer scale hole;
using plasma enhanced chemical vapor deposition (PECVD) to grow a nitride layer in the hundred nanometer scale hole and using inductively coupled plasma (ICP) to remove the nitride layer on a bottom wall of the hundred nanometer scale hole, thereby exposing a (100) crystal surface of the silicon substrate and leaving the nitride layer on a sidewall of the hundred nanometer scale hole;
using the nitride layer on the sidewall as a blocking layer and using wet etching to etch the silicon substrate exposed from the bottom wall of the hundred nanometer scale hole until exposing a tilted surface which has a (111) crystal surface; and
using metal organic chemical-vapor deposition (MOCVD) to sequentially grow an AlN buffer layer and a GaN epitaxial layer in the hundred nanometer scale hole and doping silicon into the GaN epitaxial layer to form a silicon-doped GaN epitaxial layer.
2. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein the oxide layer is grown on the silicon substrate using thermal oxidation.
3. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein the oxide layer has a thickness of 100 nm.
4. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein the sidewall of the hundred nanometer scale hole has a depth of 250-700 nm within the silicon substrate.
5. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein the sidewall is perpendicular to the (100) crystal surface.
6. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein the wet etching uses potassium hydroxide as an etching solution and etches the silicon substrate at 80° C.
7. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein the silicon-doped GaN epitaxial layer comprises cubic crystal GaN.
8. The method for fabricating the semiconductor structure having the Si substrate heterointegrated with GaN according to claim 1 , wherein in the step of doping the silicon into the GaN epitaxial layer, doping gas of silane is reacted with the GaN epitaxial layer to increase and control a concentration of doping silicon atoms into the GaN epitaxial layer when the GaN epitaxial layer is grown.