ZnMgS-based solar-blind UV photodetectors grown by MBE

Molecular beam epitaxial growth of Zn1-xMgxS alloy thin films on GaP (1 0 0 ) substrates is reported. In situ reflection high energy electron diffracti on (RHEED) studies show that the alloys can be grown with stable zinc-blend e structure up to x around 30%. For x > 30% a phase transition will occur a t a critical thickness which is sensitively dependent on the composition x. Several Schottky barrier photodetectors using Zn1-xMgxS layer, with thickn ess less than the critical thickness, as active layer were Fabricated. High ultra-violet responsivity and excellent visible rejection are achieved. Th e response curve of the Zn0.43Mg0.57S device offers a long wavelength cut-o ff at 295 nm and closely matches the erythemal action spectrum that describ es human skill sensitivity to UV radiation. (C) 2001 Elsevier Science B.V. All rights reserved.