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Mass production of high-quality semiconductor nanowire arrays (SNAs) with precisely controlled orientation and structure is essential for their application in nanoelectronics and optoelectronics. Here, we present a single-step approach for large-scale fabrication of [0001]-oriented SNAs via direct heating of their bulk components in a H2/Ar atmosphere. Real-time imaging during in-situ SEM experiments clearly demonstrates that the SNAs form through a selective vaporization process with respect to the crystallography of wurtzite crystals. We propose that the selective vaporization relies on the low symmetry of the wurtzite structure with large differences between surface energies of low-index planes. Further, we demonstrate that the approach can be extended to zinc-blende type structures through a cation exchange process. Finally, the high-quality of the SNAs is demonstrated by fabrication of photodetectors that present outstanding optoelectronic performances. We believe that our method represents a transformative new fabrication platform for large-scale fabrication of orientated SNAs with novel functionalities. Keywords: semiconductor nanowire arrays; wurtzite structure; selective vaporization