Growth and Characterisation of High Electron Mobility Transistors on 4H-SiC by Ammonia Molecular Beam Epitaxy

Abstract

The growth of GaN/AIGaN high electron mobility transistor structures (HEMT) on 4H-SiC by ammonia molecular beam epitaxy (a-MBE) is reported. Structures were grown using a magnetron sputter epitaxy deposited AlN buffer layer prior to the MBE growth of a carbon-doped insulating GaN isolation layer, undoped GaN channel layer and AIGaN cap layer. No ex-situ or in-situ high temperature pre-treatment of the SiC substrate was used. The electrical characteristics of the layers was excellent with RT mobilities of >1100 cm 2 /Vs for a sheet carrier density of >1 x 10 13 cm -2 . 2 HEMTs fabricated from layers gave an f t and f max of 36 and 80 GHz, respectively with a maximum saturated drain current of 450 mA/mm and transconductance of 160 mS/mm for a gate length of 0.3 μm.