Direct observation of contact potential distributions of wafer-bonded p-GaAs/n-GaN and p-GaAs/n-Si by scanning Kelvin probe force microscopy

Abstract

Electrical properties of the wafer bonding p-GaAs/n-GaN, p-GaAs/n-Si and p-GaAs/ITO//ITO/n-Si are investigated systematically by scanning Kelvin probe force microscopy (KPFM), capacitance–voltage (C–V) and current–voltage (I–V) measurements. By using KPFM, the contact potential distributions and contact barrier differences of these bonding heterojunctions with Schottky-like characteristics or ohmic feature have been obtained. The contact barrier differences measured by KPFM match well with those measured by C–V. These barriers indicate the thicker interface layer has a larger barrier height, which could contain more interface states. The I–V curve of the heterostructure with the smaller contact barrier difference is shown as an Ohmic contact feature. In contrast, the I–V curve of the junction with the larger contact barrier difference shows a Schottky contact behavior with a larger turn-on voltage. These behaviors indicate that the electrical conductivity of the bonding sample depends on the bonding interface layer significantly.