GaN ultraviolet avalanche photodiodes grown on 6H-SiC substrates with SiN passivation

GaN ultraviolet p-i-n avalanche photodiodes grown on 6H-SiC substrates by metalorganic chemical vapour deposition are reported. Silicon nitride (Si_xN_1-x) is employed as the dielectric passivation layer for the diode, rather than the conventional SiO₂. For the SiN passivated device, the photoresponse is relatively independent of the bias voltage for V_RB < 50 V. With ultraviolet illumination, devices with mesa diameters of ~30 mum achieve stable maximum optical gains greater than 3000. This is believed to be the first successful demonstration of GaN APDs grown on 6H-SiC substrates with optical gain greater than 1000.