| abstract |
A Group III nitride based high electron mobility transistors (HEMT) is disclosed that provides improved high frequency performance. One embodiment of the HEMT comprises a GaN buffer layer, with an Al y Ga 1−y N (y=1 or y 1) layer on the GaN buffer layer. An Al x Ga 1−x N (0≦x≦0.5) barrier layer on to the Al y Ga 1−y N layer, opposite the GaN buffer layer, Al y Ga 1−y N layer having a higher Al concentration than that of the Al x Ga 1−x N barrier layer. A preferred Al y Ga 1−y N layer has y=1 or y ˜ 1 and a preferred Al x Ga 1−x N barrier layer has 0≦x≦0.5. A 2DEG forms at the interface between the GaN buffer layer and the Al y Ga 1−y N layer. Respective source, drain and gate contacts are formed on the Al x Ga 1−x N barrier layer. The HEMT can also comprising a substrate adjacent to the buffer layer, opposite the Al y Ga 1−y N layer and a nucleation layer between the Al x Ga 1−x N buffer layer and the substrate. |