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Zn1−xMgxS alloy thin films covering Mg composition, x, from 0 to 1 were grown on GaP (100) substrates using molecular beamepitaxy. As observed by reflection high energy electron diffraction patterns, the alloys can be grown with stable zinc-blende structures up to x around 30%. For x>30%, a structural transition will occur at a critical thickness which is sensitively dependent on the composition x. Several Schottky barrier photodetectors using a Zn1−xMgxS layer with a thickness less than the critical thickness as the active layer were fabricated. The shortest cutoff wavelength achieved so far is 270 nm. Temporal response of the device shows that the photocurrent decays with a time constant as fast as 13 ns for a mesa area, of 1.5 mm2. [ABSTRACT FROM AUTHOR]

Epitaxial growth of Zn[sub 1-x]Mg[sub x]S alloy thin films on GaP(100) substrates was carried out using the molecular-beam-epitaxy technique. In situ reflection high-energy electron diffraction studies show that the alloys can be grown with a stable zinc-blende structure up to x around 30%. For x>30%, a structural transition will occur at a critical thickness which is sensitively dependent on the x composition. A near-band-edge peak with a full width at half maximum of about 10 nm was observed in room-temperature photoluminescence measurements made on as-grown alloy thin films. Several Zn[sub 1-x]Mg[sub x]S-based Schottky barrier photodetectors were fabricated. Room-temperature photoresponse measurements were performed on these detectors and abrupt long-wavelength cutoffs covering 325, 305, 295, and 270 nm were achieved for devices with Mg composition of 16%, 44%, 57%, and 75%, respectively. The response curve of the Zn[sub 0.43]Mg[sub 0.57]S device offers a close match to the erythemal action spectrum that describes human skin sensitivity to UV radiation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]