Effects of Thermal Annealing on Ni/Au Based Schottky Contacts on n-GaN


Esmer L., Akkaya A., Boyarbay B., AYYILDIZ E.

International Semiconductor Science and Technology Conference, Türkiye, 1 - 04 Aralık 2013, ss.19

  • Basıldığı Ülke: Türkiye
  • Sayfa Sayıları: ss.19

Özet

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.