AlGaN/GaN high‐electron‐mobility transistors on sapphire with Fe‐doped GaN buffer layer by MOVPE

A simple AlGaN/GaN HEMT structure without any interlayer on Fe‐doped GaN (GaN:Fe) grown by LP‐MOVPE in one single run on sapphire is demonstrated. The surface segregation of Fe in GaN occurring during growth is identified. Hall measurements yield 2DEG (two dimensional electron gas) mobilities of 1700 and 10700 cm2/Vs and sheet carrier concentrations of 5.1x1012 and 5.7x1012 cm–2 at 300 K and 20 K, respectively. Good pinch‐off current‐voltage (I D‐V D) characteristics is observed from AlGaN/GaN HEMTs. A maximum drain current density of 0.6 A/mm and a peak extrinsic transconductance of 200 mS/mm have been observed. The HEMT structure yields very good device isolation as indicated by an isolation current of ≤1 nA at 20 V. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)