MBE-grown ZnMgS ultra-violet photodetectors

Zn1-xMgxS alloy thin films covering Mg composition, x, from 0 to 1 were gro wn on GaP (100) substrates using molecular beam epitaxy. As observed by ref lection high energy electron diffraction patterns, the alloys can be grown with stable zinc-blende structures up to x around 30%. For x > 30%, a struc tural transition will occur at a critical thickness which is sensitively de pendent 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 mm(2).