ZnS-based visible-blind UV detectors: Effects of isoelectronic traps

The aim of this study is to reveal the underlying cause of the gradual turn-on characteristic of low Te containing ZnSTe Schottky barrier photodiodes. The results of photoresponse studies on ZnS, ZnSSe and ZnSTe diodes indicate that the Te isoelectronic trapping effect is responsible for the gradual turn-on characteristic of low Te containing ZnSTe Schottky barrier photodiodes. The results also reveal that the ZnSSe diode, having the advantage of being free of isoelectronic centers, is a more suitable choice for applications requiring high visible rejection power. It is demonstrated that highly UV sensitive responsivity with an abrupt long wavelength cutoff tailored to lie between 340-400 nm can be achieved in the ZnSSe diode system

Shubnikov-de Haas oscillations on molecular-beam-epitaxy-grown Hg 1-xCdxTe alloy doped with indium

Shubnikov-de Haas oscillations on the transverse resistivity ρxx and longitudinal resistivity ρzz of as-grown indium-doped alloys of Hg1-xCdxTe (0.24<x<0.34) grown by molecular-beam epitaxy on (111)B and (100) growth directions are observed in the temperature range from 1.2 to 25 K and in fields up to 12 T. The n-type density from the periodicity, the effective mass m* from the temperature dependence of the amplitude, and the Dingle temperature T D are determined from ρxx and ρzz oscillations. The oscillations establish the high Hall density which is found at low fields. The TD in ρxx is found to be higher in comparison to TD in ρzz. However, this difference decreases as the Hall density increases. The TD discrepancy is probably due to greater inhomogeneity in the plane of the layer. The T D is higher than the temperature calculated from the weak-field Hall mobility. The density and effective mass are used to calculate the energy band gap, Fermi energy, and the band-edge effective mass. The calculated energy band gaps are in good agreement with the reported results

Role of the crystallographic orientation on the incorporation of indium in HgCdTe epilayers grown by molecular beam epitaxy

In-doped HgCdTe films have been grown by molecular beam epitaxy (MBE) on CdTe substrates in the (100) crystallographic orientation. They were characterized by Hall and secondary-ion mass spectroscopy measurements. The results are compared with those of In-doped HgCdTe layers grown in the (111)B orientation. In the (111)B orientation indium is incorporated in the metal site whereas in the (100) orientation it appears that indium is mainly incorporated interstitially. The results agree with a Te antisite model as a possibility for explaining the electrical behavior of (100) HgCdTe grown by MBE

Molecular beam epitaxial growth and characterization of a novel superlattice system: Hg1-xCdxTe-CdTe

Hg1-xCdxTe-CdTe superlattices of both type I and type III have been grown for the first time using the molecular beam epitaxy technique. The superlattices were grown at 190°C. They have been characterized by electron and x-ray diffraction, infrared transmission, and Hall measurements. The presence of satellite peaks in the x-ray spectra shows the superlattices to be of high quality. Infrared transmission spectra show that HgCdTe-CdTe superlattices have narrower band gaps than equivalent HgCdTe alloys. These superlattices are p type. Their Hall characterizations, along with magnetotransport experiments, seem to indicate that high hole mobilities observed in p-type HgTe-CdTe superlattices are due to some type of relationship between the two-dimensional heavy hole gas and the interface state existing in type III superlattices