Highly sensitive ultraviolet PIN photodiodes of ZnSSe n + –i–p structure/p + ‐GaAs substrate grown by MBE

Highly sensitive and stable ultraviolet PIN photodiodes of ZnSSe junction structure on p + ‐GaAs substrates are developed by molecular beam epitaxy (MBE) growth. The short‐wavelength photodiodes are grown on p‐type (100)GaAs by MBE utilizing an optimized “hetero‐interface super‐lattice (SLE) buffer” consisting of a ZnTe–ZnSe multiple quantum well, by which a large energy barrier (>1 eV) for hole ohmic conduction is overcome. ZnSSe n + –i–p photodiodes with a thin interface SLE are grown in a complete lattice‐matched condition (S = 6%). High sensitivities of 0.30 A/W (external quantum efficiency: η = 83.6%) in the blue (450 nm), 0.24 A/W ( η = 75.8%) in the blue–violet (400 nm: for BlueRay and HD‐DVD systems) and 0.12 A/W ( η = 50.9%) in the ultraviolet (300 nm) regions are obtained with an extremely low dark leakage current (∼sub pA/mm 2 ) under high reverse bias (20 V) at 300 K. Because of the low dark current, a very low noise equivalent power value below 10 –14 W $ \sqrt {{\rm Hz/cm}^{-2}} $ (450 nm) is proved in the blue–violet region. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)