Optical characterization of GaN/SiC n-p heterojunctions and p-SiC

Abstract

Optical characterization of GaN/SiC heterojunctions and p-SiC has been performed to explain the current–voltage (I–V) characteristics in GaN/SiC n-p heterojunction diodes. The I–V characteristics exhibit tunneling-assisted current with low forward “turn-on” voltages around 1.15 V as opposed to the expected drift/diffusion current with a turn on around 2.5 V. Electroluminescence (EL) measurements on these diodes revealed an infrared peak at 1.25 eV and a red peak at 1.75 eV. Photoluminescence (PL) measurements on p-SiC yielded peaks at 1.25 and 1.80 eV. Since the band gap of 6H–SiC is 3.03 eV, we attribute the EL and PL peaks to radiative transitions from the conduction band edge to a defect level and subsequently down to the valence band edge of p-SiC. This defect level is located 1.25 eV above the valence band edge.