Photoresponse studies of ZnSSe visible-blind ultraviolet detectors: A comparison to ZnSTe detectors

This work focuses on the investigation of the difference between the photor esponse of ZnS, ZnSSe, and that of ZnSTe Schottky-barrier photodiodes, with a particular aim to reveal the underlying causes of the gradual turn-on ch aracteristic of low-Te-containing ZnSTe Schottky barrier photodiodes. To fo rm the bottom electrode layer for the newly developed ZnSSe diode, n-type d oping of ZnSSe by incorporating Al flux during molecular beam epitaxial gro wth was studied. Excellent-to-good dopant activation is achieved for Se com position up to 50%. The measured photoresponse of the diodes clearly indica tes that the Te isoelectronic trapping effect is responsible for the gradua l turn-on characteristic of low-Te-containing ZnSTe Schottky-barrier photod iodes. The results also reveal that the ZnSSe diode, having a much better v isible rejection power, is a more suitable choice for high-performance visi ble-blind ultraviolet detection applications. (C) 1999 American Institute o f Physics. [S0003-6951(99)03949-2].