Ge Mediated Surface Preparation for Twin Free 3C-SiC Nucleation and Growth on Low Off-Axis 4H-SiC Substrate

In this work, we report on the effect of adding GeH4 during 3C-SiC heteroepitaxial growth on low off-axis 4H-SiC substrate using chemical vapor deposition technique. When added together with SiH4 and C3H8, GeH4 does not significantly modify the 3C layer quality which contains a high density of twin boundaries. But when it is introduced before the growth, i.e. during a surface pretreatment step at 1500 degrees C, a remarkable change in the layer morphology is seen. Furthermore for optimal GeH4 flux, twin boundaries are completely eliminated. Investigation of the results obtained when varying growth parameters (temperature, C/Si ratio, gas composition during the surface preparation) allowed proposing a mechanism leading to twin boundary elimination. It involves a transient homoepitaxial growth step followed by 3C nucleation when large terraces are formed by step faceting. Preliminary electrical characterizations of the twin free 3C-SiC layers, using conductive atomic force microscopy (c-AFM), are given. (C) 2014 The Electrochemical Society. All rights reserved.