Organometallic vapor-phase-epitaxial growth and characterization of ZnGeAs2 on GaAs

Abstract

We report the epitaxial growth of single-crystal stoichiometric ZnGeAs2. The (001) ZnGeAs2 layers were deposited by organometallic vapor-phase epitaxy on (100) GaAs. The epitaxy has specular surface morphology. The stoichiometric chemical composition has been confirmed by x-ray diffraction, electron microprobe, and Auger electron spectroscopy. Selected-area electron diffraction patterns clearly indicate the chalcopyrite structure and that the [001] lattice direction is the growth direction. X-ray diffraction indicates that the c-direction lattice constant is 11.192 Å for our epitaxial material, which is an elongation of 0.35% from the bulk material value of 11.153 Å. When stiffness constants for ZnGeAs2 are approximated by those of GaAs, this c-axis elongation can be explained by a contraction in the a direction induced by the 3.4×10−3 lattice mismatch between the ZnGeAs2 epitaxy and the GaAs substrate. Absorptance and transmittance measurements indicate that this material has a direct band gap of approximately 1.15 eV and agrees well with previously reported values. Hall measurements show that the material is p type with room-temperature hole mobilities up to 56 cm2 V−1 s−1 for a corresponding carrier concentration of 9×1018 cm−3. This mobility is slightly higher than previously reported for bulk material and attests to the high quality of this material.