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 μ
n
was used as a parameter to fit the
J
_F
-
V
_F
characteristics of both reported and fabricated GaN SBDs. At 300 K, μ
n
was fitted to be 600 cm
²
/V ·s when electron concentration
n
was 1 × 10
¹⁶
cm
^-3
and 750 cm
²
/V ·s when
n
was 5 ×10
¹⁵
cm
^-3
. Accordingly, the theoretical μ
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.