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

摘要

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 $hbox{cm}^{2}/hbox{V} cdot hbox{s}$ when electron concentration $n$ was $hbox{1} timesbreak hbox{10}^{16} hbox{cm}^{-3}$ and 750 $hbox{cm}^{2}/hbox{V} cdot hbox{s}$ when $n$ was $hbox{5} times hbox{10}^{15} hbox{cm}^{-3}$. 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 -n-ncarrier lifetimes in the high-injection region and with Shockley–Read–Hall lifetimes in the generation–recombination current region.