Numerical Analysis of Forward-Current/Voltage Characteristics of Vertical GaN Schottky-Barrier Diodes and p-n Diodes on Free-Standing GaN Substrates

Forward-current-density J(F)/forward-voltage V-F characteristics of vertical gallium-nitride (GaN) Schottky-barrier diodes (SBDs) and p-n diodes on free-standing GaN substrates were computationally, as well as experimentally, investigated. Based on the thermionic emission model, electron-drift mobility mu(n) was used as a parameter to fit the J(F)-V-F characteristics of both reported and fabricated GaN SBDs. At 300 K, mu(n) was fitted to be 600 cm(2)/V . s when electron concentration n was 1 x 10(16) cm(-3) and 750 cm(2)/V . s when n was 5 x 10(15) cm(-3). Accordingly, the theoretical mu(n)-n curve for a carrier compensation ratio of 0.90 was applied in the case of n-GaN layers on GaN substrates. With respect to GaN p-n diodes, the reported J(F)-V-F characteristics were successfully fitted with dislocation-mediated carrier lifetimes in the high-injection region and with Shockley-Read-Hall lifetimes in the generation-recombination current region.