A high-field operation of p+–n structure blue-ultraviolet photodetectors has been studied using ZnSe-based II–VI wide-band-gap compound semiconductors grown by molecular-beam epitaxy (MBE). With an improved crystal quality on macrodefects (dislocations and stacking faults) during an initial MBE growth as well as an optimized device structure including a complete superlattice ohmic-contact layer, a stable high electric-field operation up to 8×105 V/cm is established. It is demonstrated that the p+–n ZnSe photodiodes have shown a stable avalanche-photodiode operation with a large avalanche gain of G=60 in the blue-ultraviolet region at room temperature.

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Subject classification: 68.55. Ln; 72.40.+w; 81.15.Hi; 85.60.Dw; 85.60.Gz; S8.12; S8.15 II-VI ZnSe (binary) and ZnSSe (ternary) widegap compound semiconductor based photovoltaic devices (p-i-n and avalanche photodiodes (APDs)) are developed for the blue-violet (460-400 nm) optical wavelength region by molecular beam epitaxial (MBE) growth. The ternary compound ZnSSe p-i-n structure photodiodes, grown with complete lattice matched condition on GaAs substrates, exhibit high external quantum efficiencies of 80-70% in the blue-violet optical region with extremely low dark currents (~pA/mm 2 ), These diodes reveal stable and long-lived operation at 300 K. Also presented is ZnSe and ZnSSe based blue-violet APD devices, fabricated by precise defect control and process techniques. This new device has revealed large signal gain (G) of G = 50 for ZnSe, and G = 60 for the ZnSSe APD device under high electric field strength of (0.8-1.1) Â 10 6 V/cm. Important device parameters, ionization coefficients of photo-injected electrons and holes, and device stability are also discussed.