We report studies on the role of a ZnTe buffer in determining the crystalline phase of MBE-grown MnSe_1−xTe_x alloy thin films. It was found that MBE growth of MnSe and MnTe directly onto a zincblende GaAs substrate usually result in their corresponding stable phases, which are rocksalt and hexagonal, respectively. A set of zincblende MnSe_1−xTe_x alloy thin films with Te composition covering from 0.27 to 1 were fabricated on zincblende ZnTe buffer layers. We have addressed the lattice distortion issue due to thin film effect for these films. A combination of several structural characterizations demonstrates that a perfect lattice matched MnSe_1−xTe_x/ZnTe heterostructure can indeed be realized. The results of this study pave the way for realizing a double-barrier MnSe_1−xTe_x/ZnTe/MnSe_1−xTe_x resonant tunneling diod structure with perfect lattice match as a candidate for a promising THz emitter.