Growth of ZnSe/GaAs and ZnSe/Ge heterostructures by atmospheric pressure metalorganic chemical vapor deposition method
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The objective of the present research is to grow and characterize Zinc- Selenide (ZnSe) material on different substrates, namely Gallium Arsenide (GaAs) and Germanium (Ge), using the Metalorganic Chemical Vapor Deposition (MOCVD) technique. A MOCVD system is built for this purpose. The surface morphology of the grown layers is examined using the Digital Equipment contact mode atomic force microscope (AFM). The carrier concentration-depth profiles are obtained for ZnSe/Ge heterostructure using the Bio-Rad electrochemical CV profiler. The surface morphology of the ZnSe epilayer grown on [111 ] GaAs substrates was found to be very rough, where the grown material is believed to be polycrystalline. The quality of the ZnSe surface, however, was improved when  GaAs substrates were used. The surface was improved even further when the surface of the GaAs was saturated with zinc, before growing the ZnSe layer. Expecting to achieve the same results with Ge substrates, the surfaces of one sample was saturated with zinc and another sample with selenide. The best surface morphology was found to be the sample whose surface was first saturated with selenide. In the carrier concentration-depth profile, doping changes abruptly from n to p at 1.5 pm. This indicates that the ZnSe layer is 1.5 pm thick since the ZnSe is expected to be n-type and the Ge is a p-type material. This means the growth rate of ZnSe on Ge is about 500?A/min, if 1 seem flow rate for Zn and Se are used with the substrate temperature held at 300?C.