Au–Ag binary alloys on n-GaAs substrates and effect of work functions on Schottky barrier height

Abdullah Akkaya

doi:10.1007/s10854-021-06276-9

Abstract

In this study, I investigated the effect of work function (ϕm) of AuxAg1−x (x = 0, 0.22, 0.37, 0.71 and 1) on the Au–Ag/n-GaAs Schottky diode (SD) parameters. Ag, Au metals and three alloys with different compositions deposited on n-GaAs substrates by the thermal evaporation method. Surface morphologies of the samples were investigated by an atomic force microscope (AFM). Elemental compositions of Schottky contact metals were conducted by energy dispersive X-ray spectroscopy (EDX). Current–voltage (I–V) and capacitance–voltage (C–V) measurements were performed at room temperature. SD parameters such as barrier height (Φb0), ideality factor (n), series resistance (Rs), and interface state density (Dit) of the SD’s were calculated from the obtained I–V and C–V data. Experimental results showed that all calculated SD parameters depend on the alloy composition. The lowest mean barrier height value was found as 0.789 ± 0.022 eV for Au/n-GaAs SDs and the highest value was determined 0.847 ± 0.008 eV for Au0.71Ag0.29/n-GaAs SDs from I–V measurements. Weak dependencies of barrier height to ϕm existed and gap state parameter (S) determined as 0.0526. The S value was close to the Bardeen limit (S = 0) and indicates that the Fermi level was strongly pinned in Au–Ag/n-GaAs SDs. Also, main SD parameters like series resistance (Rs), ideality factor (n), reverse bias barrier height (ΦbRB), doping density (Nd) and density of interface states (Dit) were calculated via using different methods from I–V and C–V measurement results. Also, to determine the leakage current mechanism Poole–Frenkel emission (PFE) and Schottky emission (SE) models applied on reverse bias I–V data.

Highlights

Barrier formation mechanisms of metal-semiconductor contacts have been a major research topic since the first discovery of these contacts [1,2,3,4]
Here; V0 is related with the built-in potential Vbi by the equation Vbi=V0+kT/q and barrier height were given by equation [7], ΦbCV = Vbi + Vn where, Vn is the potential difference between the bottom of the conduction band and the Fermi level in the neutral region of n-GaAs and Vn=(kT/q) ln(Nc/Nd), where Nc is the temperature dependent density of states in the conduction band and its value was calculated from the Nc=2(2πm*⁄kT/h2)3/2, and m*=0.063m0, and found 4.573x1017 cm-3 for GaAs at 300 K
Au-Ag/n-GaAs Schottky diode (SD) fabricated by thermal evaporation method and investigated the effect of work function of metals on SD’s parameters

Summary

Introduction

Barrier formation mechanisms of metal-semiconductor contacts have been a major research topic since the first discovery of these contacts [1,2,3,4]. SD parameters such as barrier height (Φb0), ideality factor (n), series resistance (Rs), and interface state density (Dit) of the SD’s were calculated from the obtained I-V and C-V data.

Results

Conclusion