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

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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.