Simulation and electrical characterization of GaN/SiC and AlGaN/SiC heterodiodes

Heterojunctions on SIC is an area in rapid development, especially GaN/SiC and AlGaN/SiC heterojunctions. The heterojunction can improve the performan ce considerably for BJTs and FETs. In this work heterojunction diodes have been manufactured and characterized. The structure was a GaN or AlGaN n-typ e region on top of a 6H-SiC p-type substrate. Two different approaches of g rowing the a-type region were tested. The GaN was grown with the MBE techni que using a polycrystalline GaN buffer, whereas the AlGaN was grown with CV D and an AIN buffer. The AIGaN had an aluminum mole fraction of around 0.1. Mesa structures were formed using Cl-2 RIE of GaN/AlGaN, which showed good selectivity on 6H-SiC (about I:6). A Ti metallization with subsequent RTA was used as contact to GaN and AlGaN, and the contact to 6H-SiC was liquid InGa. Both I-V and C-V measurements were performed on the heterojunction di ode. The ideality factor of the diodes. doping concentration of the SiC, an d the band alignment of the heterojunction were extracted. (C) 1999 Elsevie r Science S.A. All rights reserved.