High quantum efficiency II–VI photodetectors for the blue and blue-violet spectral range

Abstract

We have fabricated II–VI wide gap hetero PIN photodiodes made of ZnMgSSe with excellent structural and interface quality and with a high external quantum efficiency of about 60%, which is close to the theoretical limit. The internal quantum efficiency reaches peak values of more than 80%. The onset of the sensitivity is very sharp, leading to a quantum efficiency less than 10−4 at wavelength 60 nm below the band gap. Using the wide range of energy gaps from 2.68 to 3.1 eV, it is possible to fabricate wavelength selective detectors if the energy gap of the top p-type layer is chosen slightly higher than that of the intrinsic zone. The dark current is below 0.1 pA/mm2. In the low signal limit, the noise equivalent power can be estimated to be below 10−15 WHz/mm2 at the peak external quantum efficiency, surpassing ultraviolet optimized Si detectors.

Wide-bandgap semiconductor ultraviolet photodetectors

“…There have been reports of p-i-n photodiodes based on ZnSe [Ger98,Hon98,Ish00], ZnMgSSe [Ehi98] and ZnMgBeSe [Sie99,Vig01b]. With these structures, peak responsivities of 0.23 A W −1 at 460 nm (ZnSe) to 0.2 A W −1 at 430 nm and 0.22 A W −1 at 430 nm (ZnMgBeSe) are obtained.…”

Localization of excitons in Zn1−Mg Se and Cd1−Mg Se crystals

“…Ternary alloys Zn 1−x Mg x Se and Cd 1−x Mg x Se, studied in this work, are components of ZnCdSe/ZnCdMgSe and BeCdSe/ZnCdMgSe quantum wells heterostructures which are lattice matched to InP and are very promising for construction of visible light emitting diodes [1,2] and Bragg reflectors [3]. Visible-blind ultraviolet detectors based on ZnMgBeSe [4] and photodetectors for blue-violet spectral range based ZnMgSSe [5] have already been demonstrated.…”

High-efficiency p–i–n detectors for the visible spectral range based on ZnSTe–ZnTe superlattices

“…1 Comparable values for silicon devices optimized for the same spectral range but without antireflection coating are about 50%, the losses being nearly exclusively due to reflection. The external quantum efficiencies for all ZnS 0.2 Te/ZnTe superlattice devices lie in the range between 10% and 70%.…”

“…1 However, these ZnSe-based devices are only sensitive in the blue and near-UV range of the spectrum, and it would be highly desirable to have an alternative material that covers a larger part of the visible spectrum. For ZnMgSSe p -i -n detectors, we demonstrated that internal quantum efficiencies close to unity can be reached even for very thin devices, and that the dark currents, and consequently, the signal-to-noise ratio, of these devices can be considerably lower than in silicon.…”