Effects of ad-atom stoichiometry and stacking faults nucleation on the structure and morphology of MOVPE-grown (100)ZnTe homoepitaxial layers

ZnTe with its 2.26 eV (548.5 nm) direct gap at RT, is an ideal semiconductor for fabrication of efficient light emitting diodes and lasers operating in the pure green region of the visible light (540-580 nm). Until few years ago, the lack of high-quality ZnTe single crystal wafers forced the growth of ZnTe and related alloys on III-V substrates (namely GaAs) leading to severe structural problems, preventing the realisation of device-quality heterostructures. This limitation has been recently overcome, as high quality ZnTe substrates, grown by VGF method, became available [1]. Still, substrate preparation and MOVPE growth conditions remain critical steps in the fabrication of high quality ZnTe homoepitaxial layers. We have previously reported on the effects of in-situ H2 annealing of the ZnTe substrate surface on the overall crystalline quality of the ZnTe epilayers. In the present work we further demonstrate that the micro-crystalline structure and surface morphology of ZnTe epilayers grown by atmospheric pressure MOVPE on high quality VGF-grown (100)ZnTe:P wafers result from the complex interplay between surface ad-atom stoichiometry during the growth and stacking faults (SFs) nucleation at the epilayer-substrate homo-interface.