Molecular beam epitaxy and morphological studies of homoepitaxial layers on chemical mechanical polished InSb(100) and InSb(111)B substrates

Abstract

Noncontact atomic force microscopy (AFM) has been used to assess the surface morphology and structure of InSb homoepitaxial layers grown on chemical mechanical polished (CMP) InSb(100) and InSb(111)B surfaces. Although it is difficult to grow epilayers on highly conducting InSb substrates, this work demonstrates the ability to grow layers with an average roughness (Ra) of 5.7Å on 2×1018 n-type InSb(100) surfaces. Furthermore on 7×1014 n-type InSb(111)B surfaces, extremely flat layers with Ra’s of approximately 1.7Å were grown. Thermal x-ray photoelectron spectroscopy was implemented to analyze surface oxide desorption on the CMP prepared “epiready” wafers. Sb to In flux ratio and substrate deposition temperature are critical in obtaining high quality epitaxial material. For the InSb(100) surfaces, an Sb∕In flux ratio of 1.5:1, a substrate temperature of 380°C, and a background pressure of 1×10−10Torr produced smooth surfaces. For InSb(111)B surfaces, a ratio of 7:1 and a substrate temperature of 380°C at a similar background pressure produced smooth surfaces. Higher flux ratios resulted in atomically rough surfaces. The homoepitaxy formation of an ordered step terrace surface was confirmed with AFM on both epiready CMP prepared InSb crystal surfaces.