Low on‐resistance of GaN p‐i‐n vertical conducting diodes grown on 4H‐SiC substrates

Abstract

AbstractWe investigated the resistance of conductive AlGaN buffer layers and the current‐voltage characteristics of GaN p‐i‐n vertical conducting diodes on n‐type 4H‐SiC substrates grown by low‐pressure metalorganic vapor‐phase epitaxy. High Si doping of the AlGaN buffer layer at the AlGaN/SiC interface produces ohmic current‐voltage characteristics in spite of the large band offset between AlGaN and 4H‐SiC. Owing to the optimization of the AlGaN buffer layer, a low on‐resistance (Ron) of 1.12 mΩ cm2 with high breakdown voltage (VB) of 300 V is obtained for a GaN p‐i‐n vertical conducting diode on a 4H‐SiC substrate, leading to the figure of merit (VB2/Ron) of 80 MW/cm2, which is larger than that for the diode with the same structure on a 6H‐SiC substrate (62 MW/cm2). This result indicates that 4H‐SiC is preferable for fabricating GaN‐based electronic devices with a low on‐resistance and high breakdown voltage. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)