Wavelength selective wide bandgap II-VI detectors

In modern technology there is a growing demand for wavelength selective, highly sensitive detectors in the visible spectral range, especially for short wavelengths. II-VI wide gap PIN photodiodes have been fabricated using ZnMgSSe and ZnSTe heterostructures grown by molecular beam epitaxy (MBE). These diodes have excellent structural and interface quality and a high external quantum efficiency (QE) of up to 60%, which is dose to the theoretical limit. Devices which use a p-type layer as a "built in band edge filter" for wavelengths shorter than the energy gap have a spectral response with a full width at half maximum (FWHM) down to 6.5 nn and a QE of 10%. The shape of the spectral response and the stray signal rejection is comparable to metal-dielectric type bandpass filters with an optical density of 4 for the ultraviolet. Due to the high external QE and a low dark current below 0.1 pA/mm/sup 2/, II-VI wide gap hetero PIN photodiodes surpass UV optimized Si detectors and filter detector combinations with bandwidths between 20 nm and 80 nm in detectivity in the UV spectral range.