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

Forward-current-densityJF/forward-voltageVFcharacteristics 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 μnwas used as a parameter to fit theJF-VFcharacteristics of both reported and fabricated GaN SBDs. At 300 K, μnwas fitted to be 600 cm2/V ·s when electron concentrationnwas 1 × 1016cm-3and 750 cm2/V ·s whennwas 5 ×1015cm-3. Accordingly, the theoretical μn-ncurve 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 reportedJF-VFcharacteristics 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.