Quantitative analysis of backscattered electron (BSE) contrast using low voltage scanning electron microscopy (LVSEM) and its application to Al0.22Ga0.78N/GaN layers

A novel method to quantify and predict the material contrast using Backscattered Electron (BSE) imaging in Scanning Electron Microscopy (SEM) is presented while using low primary electron beam energies (Ep). In this study, the parameters for BSE imaging in Low Voltage Scanning Electron Microscopy (LVSEM) are optimized for the layer system Al0.22Ga0.78N/GaN, which is typically used in High Electron Mobility Transistors (HEMTs). The layers are imaged at high resolution and the compounds are identified based on the quantitative BSE material contrast between Al0.22Ga0.78N and GaN. The quantification process described in this study is based on an analytical description that predicts the material contrast using a function that correlates the effective backscattering coefficient (η) with the atomic number Z.