High performance AlGaN/GaN HEMTs with recessed gate on sapphire substrate

A high performance AlGaN/GaN high electron mobility transistor (HEMT) with recessed gate is successfully fabricated on a sapphire substrate. In order to realize a high performance HEMT, it is very important not only to improve the 2-dimensional electron gas (2DEG) but also to reduce the parasitic resistance. However, the increase of aluminum content in AlGaN to produce a high density 2DEG results in poor ohmic contact, as well known. In our recessed gate structure, an ohmic contact with low resistivity can be formed on n-GaN with high electron density. This is grown on an AlGaN layer with high aluminum content. We describe the fabrication and illustrate the performance of the AlGaN/GaN HEMT with recessed gate and conclude that it is a promising device for high power and high frequency applications.