Anisotropy effects on the performance of wurtzite GaN impact-ionization-avalanche-transit-time diodes

Abstract

We demonstrate that a GaN impact-ionization-avalanche-transit-time (IMPATT) diode exhibits a higher frequency and a wider bandwidth in the basal plane (Γ–M direction) than along the c-axis (Γ–A direction). Because of the better efficiency, RF power, and negative resistance performance at a high frequency, the use of the diode in the Γ–M direction is more appropriate for high-frequency operation. In addition, the diodes are cut off when the specific contact resistances are ∼10−6 and ∼10−5 Ω·cm2. Thus, the very high specific contact resistance of p-type GaN of about ∼10−4 Ω·cm2 provides an important limitation to the fabrication of pn junction GaN IMPATT diodes.