CdTe/GaAs(100) heterojunctions: Growth modification by thin silicon interface layers

Abstract

The growth of CdTe epilayers on GaAs has been explored as a potential buffer layer for the fabrication of CMT/CdTe/GaAs structures on silicon substrates. CdTe layers were deposited by molecular beam epitaxy onto GaAs(100) specimens transferred into the II–VI reactor protected by an amorphous arsenic (a-As) cap. Reflection high energy electron diffraction and double- crystal-x-ray diffraction studies show that CdTe{111} layers grow epitaxially on both As- and Ga-rich GaAs(100) surfaces. The relatively narrow x-ray linewidths associated with the layers demonstrate that the layers are of high structural quality. The detailed nature of the interface between CdTe and GaAs has been studied by x-ray photoemission spectroscopy and low energy electron diffraction. It is shown that the interface is highly reactive, leading to the formation of gallium telluride, which influences the growth orientation of the CdTe layer. In an attempt to prevent such interface chemical reactions, we have explored the use of ultrathin silicon interface layers. Thus, GaAs(100) substrates were covered with 1 ML of Si before being capped with a-As. The samples were transferred to a surface science spectrometer, where the a-As cap was removed, producing an ordered Si-(3×1)/GaAs(100) surface. The subsequent growth of CdTe on the Si/GaAs(100) samples yielded well-ordered epilayers, always displaying the (100) orientation. Possible reasons for the change in epilayer crystallographic orientation due to the presence of the Si interlayer are considered.