Akademik Veri Yönetim Sistemi
International Semiconductor Science and Technology Conference, Türkiye, 1 - 04 Aralık 2013, ss.19
Recent developments in GaN based devices have revealed them to be strong candidates for
future high power devices with high frequency operation. In the present work, we have
investigated the effect of thermal annealing on the electrical and structural properties of Ni/Au
Schottky contacts to n-type GaN. The Schottky contacts were fabricated by lift-off lithography
using Ni/Au metallization on GaN grown by metal organic chemical vapor deposition (MOCVD)
on a (0001) sapphire substrate. Electrical properties including current-voltage (I-V) and
capacitance-voltage (C-V) characteristics were measured on the Ni based Schottky contacts as a
function of annealing temperature. Annealing treatment was performed at a temperature ranging
from 100 to 800 °C in increments of 100 °C for 2 min. The Schottky barrier heights (SBHs) for
these contacts were obtained from I-V and C-V measurements. The values of SBH obtained from
the C-V measurements were found to be higher than that of obtained from the I-V measurements.
This case was attributed to the presence of the lateral inhomogeneities of the barrier height. It was
seen that the SBH slightly increased from 0.560?0.004 eV (as-deposed sample) to 0.563±0.006 eV
(annealed at 500 °C). The SBH of the Ni/Au Schottky contact for the other annealing temperatures
of 600 °C was 0.617±0.005 eV. The highest SBH was obtained for Ni/Au Schottky contact after
annealing at 700 °C and the value was 0.910±0.019 eV. The failure of rectifying behavior at high
temperature annealing may be due to the interfacial reaction between Ni/Au and GaN layer. The
variations in the chemical composition of the contacts with the annealing process were examined
by XPS depth profile analysis. Increment in barrier height by as much as % 62.5 was successfully
recorded by thermal annealing at 700ºC and it was concluded that this technique was promising
for high power GaN electronics.