Molecular beam epitaxy and characterizations of PbTe grown on GaAs(211) substrates using CdTe/ZnTe buffers

Abstract

Narrow-gap semiconductor PbTe has exhibited versatility in both mid-infrared optoelelctronics and thermoelectrics. However, the absence of commercially obtainable PbTe crystal substrates limits its wide applications. In this paper, heteroepitaxy of high-quality PbTe crystal on GaAs(211) using CdTe/ZnTe buffers by molecular beam epitaxy is presented for the first time. Optimal growth parameters have been obtained by both in-situ and ex-situ characterizations. In-situ reflection high-energy electron diffraction observed a transition of growth mode from 2D to 3D, which is in agreement with the results of atomic force microscope and scanning electron microscope characterizations. High resolution X-ray diffraction revealed that the growth of PbTe crystal is along [531] direction which is different from the [211] substrate orientation. Multiple phonon modes related to PbTe were observed by Raman scattering while mid-infrared light emission from epitaxial PbTe is observed at a peak of 3.5μm by photoluminescence. Different from PbTe grown on BaF2(111), n-type conductivity with electron densities of ~5×1017cm−3 and mobilities of 675cm2/Vs at room temperature and 4300cm2/Vs at 2K is observed. The high quality PbTe grown on GaAs(211) substrates using CdTe/ZnTe buffers renders promising applications in both optoelectronics and thermoelectrics.