Highly Efficient Blue-Ultraviolet Photodetectors Based on II-VI Wide-Bandgap Compound Semiconductors

Abstract

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/mm2), 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) × 106 V/cm. Important device parameters, ionization coefficients of photo-injected electrons and holes, and device stability are also discussed.