Abstract
Properties of metalorganic-chemical-vapor-deposition-grown AlGaN/GaN hetero-structures on sapphire substrates were studied by the Hall effect and atomic force microscopy. The effects of the Al composition and roughness of the surface on the two dimensional electron gas (2DEG) mobility were investigated. 2DEG mobility of undoped-Al0.11Ga0.89N/GaN heterostructure on sapphire was 1100 and 9260cm2/V-s at 300K and 4.6K, respectively. We also fabricated recessed gate and non-recessed gate AlGaN/GaN high electron mobility transistors (HEMT). The recessed and non-recessed gate devices showed the maximum transconductance 146 and 93mS/mm, and drain-source current 900 and 720mA/mm, respectively. The recessed gate AlGaN/GaN HEMT exhibited the very weak temperature dependence of the threshold voltage. Our results demonstrate significant performance improvement for AlGaN/GaN HEMT by using recessed-gate.
