High electron mobility transistor
According to an embodiment of the present invention, a high electron mobility transistor (HEMT) includes: a buffer layer on a substrate; a carrier transit layer on the buffer layer; a carrier supply layer on the carrier transit layer; a gate electrode on the carrier supply layer; and a source and a drain adjacent to two sides of the gate electrode. Preferably, the carrier supply layer comprises a concentration gradient of aluminum (Al).
1. A high electron mobility transistor (HEMT), comprising:
a buffer layer on a substrate;
a carrier transit layer on the buffer layer;
a carrier supply layer on the carrier transit layer, wherein the carrier supply layer comprises a concentration gradient of aluminum (Al) and a concentration of Al decreases toward a boundary between the carrier transit layer and the carrier supply layer;
a gate electrode on the carrier supply layer; and
a source electrode and a drain electrode adjacent to two sides of the gate electrode.
2. The HEMT of claim 1 , wherein the buffer layer comprises gallium nitride (GaN).
3. The HEMT of claim 1 , wherein the carrier transit layer comprises unintentionally doped (UID) GaN.
4. The HEMT of claim 1 , wherein the carrier supply layer comprises n-type Al x Ga 1-x N.
5. The HEMT of claim 1 , wherein the carrier supply layer is doped with silicon or germanium.
6. The HEMT of claim 1 , wherein carrier supply layer comprises an epitaxial layer.
7. The HEMT of claim 1 , wherein bottom surfaces of the carrier supply layer and the source electrode and the drain electrode are coplanar.
8. A high electron mobility transistor (HEMT), comprising:
a buffer layer on a substrate;
a carrier transit layer on the buffer layer;
a carrier supply layer on the carrier transit layer;
a gate electrode on the carrier supply layer, wherein the gate electrode comprises a top portion and a bottom portion, the top portion and the bottom portion comprise different materials, and the top portion comprises metal and the bottom portion comprises an epitaxial layer; and
a source electrode and a drain electrode adjacent to two sides of the gate electrode.
9. The HEMT of claim 8 , wherein the buffer layer comprises gallium nitride (GaN).
10. The HEMT of claim 8 , wherein the carrier transit layer comprises unintentionally doped (UID) GaN.
11. The HEMT of claim 8 , wherein the carrier supply layer comprises n-type Al x Ga 1-x N.
12. The HEMT of claim 8 , wherein the carrier supply layer is doped with silicon or germanium.
13. The HEMT of claim 8 , wherein the carrier supply layer comprises an epitaxial layer.
14. The HEMT of claim 8 , wherein the bottom portion comprises p-type Al y Ga 1-y N.
15. The HEMT of claim 8 , wherein the bottom portion is doped with Mg or Zn.
16. The HEMT of claim 8 , wherein a thickness of the bottom portion is less than a thickness of the top portion.
17. The HEMT of claim 8 , wherein a sidewall of the top portion is aligned with a sidewall of the bottom portion.
18. The HEMT of claim 8 , wherein bottom surfaces of the carrier supply layer and the source electrode and the drain electrode are coplanar.