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 μn was used as a parameter to fit the J_F-V_F characteristics of both reported and fabricated GaN SBDs. At 300 K, μn was fitted to be 600 cm²/V ·s when electron concentration n was 1 × 10¹⁶ cm^-3 and 750 cm²/V ·s when n was 5 ×10¹⁵ cm^-3. Accordingly, the theoretical μn-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.