Polytype hetero-interface high electron mobility device and method of making
View Patent ↗A high electron mobility device and method of making is provided whereby a two-dimensional electron gas is formed at a hetero-junction or hetero-interface between different polytypes of a semiconductor material. The different crystal forms or polytypes of the semiconductor material having different electronic bandgaps are used to provide the bandgap necessary to form the two-dimensional electron gas.
1. A high electron mobility device comprising:
a substrate of semiconductor material;
a first layer of a first polytype of the semiconductor material on the substrate, the first layer being an off-axis layer and having a narrow mesa region that extends from a first main surface of the first layer;
a regrown layer of the first polytype over the narrow mesa region, the regrown layer having an on-axis surface over a top surface of the narrow mesa region;
a source region in the regrown layer over a first sidewall of the narrow mesa region;
a drain region in the regrown layer over a second sidewall of the narrow mesa region; and
a second layer of a second polytype of the semiconductor material on the regrown layer, wherein a hetero-interface is formed between the regrown layer and the second layer over the top surface of the narrow mesa region,
wherein the second layer over the top surface of the narrow mesa region is substantially a single crystal domain of the second polytype.
2. The high electron mobility device of claim 1 , wherein the semiconductor material is silicon carbide.
3. The high electron mobility device of claim 2 , wherein the second layer is on an Si-face of the regrown layer.
4. The high electron mobility device of claim 2 , wherein the second layer is on a C-face of the regrown layer.
5. The high electron mobility device of claim 1 , wherein the first polytype has a bandgap and the second polytype has a bandgap different than the bandgap of the first polytype, the polytype with the larger bandgap having impurities implanted therein.
6. The high electron mobility device of claim 1 , wherein a thickness of the second layer is selected to provide a predetermined strain across the second layer, to supply desired piezocharge to the hetero-interface.
7. The high electron mobility device of claim 1 , wherein the first polytype is 4H, and the second polytype is 3C.
8. The high electron mobility device of claim 1 , wherein the first polytype is 6H, and the second polytype is 3C.
9. The high electron mobility device of claim 1 , wherein the first polytype is 15R, and the second polytype is 3C.
10. The high electron mobility device of claim 1 , wherein the first polytype is 4H, and the second polytype is one of 6H, 15R and 3C.
11. The electron mobility device of claim 1 , wherein a channel length between the source region and the drain region is less than about 10 microns.