Victor N. Ovsyuk

A series of silicon multiplexers for HgCdTe photodiodes of the 8-16-μm spectral range

This paper presents the results of the development of linear (1×288, 1×576) and two-dimensional (128×128, 320×256) silicon multiplexer arrays for HgCdTe photodiodes of the 8-16μm spectral range. Typical parameters of the multiplexers are given, along with the characteristics of long-wavelength hybrid IR photodetectors created at the Institute of Semiconductor Physics of the Siberian Section of the Russian Academy of Sciences.

The 4×288 linear FPA on the heteroepitaxial Hg 1-x Cd x Te base

x4×288 heteroepitaxial mercury-cadmium telluride (MCT) linear arrays for long wavelength infrared (LWIR) applications with 28×25 micron diodes and charge coupled devices (CCD) silicon readouts were designed, manufactured and tested. MCT heteroepitaxial layers were grown by MBE technology on (013) GaAs substrates with CdZnTe buffer layers and have cutoff wavelength λco ≈ 11.8 μm at T = 78 K. To decrease the surface influence of the carriers recombination processes the layers with composition changes and its increase both toward the surface and HgCdTe/CdZnTe boundary were grown. Silicon read-outs with CCD multiplexers with input direct injection circuits were designed, manufactured and tested. The testing procedure to qualify read-out integrated circuits (ROICs) on wafer level at T = 300 K was worked out. The silicon read-outs for 4×288 arrays, with skimming and partitioning functions included were manufactured by n-channel MOS technology with buried or surface channel CCD register. Designed CCD readouts are driven with four- or two-phase clock pulses. The HgCdTe arrays and Si CCD readouts were hybridized by cold welding indium bumps technology. With skimming mode used for 4×288 MCT n-p-junctions, the detectivity was about (formula available in paper) for background temperature Tb = 295 K.

Infrared photoconductors fabricated on Hg1-xCdxTe film grown by molecular beam epitaxy

We used the heterostructures of HgCdTe/CdZnTe/GaAs grown by molecular beam epitaxy for fabrication of photoconductor devices. The composition of MCT films throughout the thickness was controlled in situ by ellipsometry during the growth process. There were wide band gap layers at the interface and at the surface of the MCT films for decreasing the surface recombination which strongly influences on devices characteristics. The use of n-type material for LWIR photoconductors (77 K, the cutoff wavelength is more than 13 mkm) with good performance was demonstrated. The detectivity in maximum of wavelength dependence varies in interval (1.5 divided by 5)(DOT)1010 cmHz1/2 W-1. P-type material was used for MWIR photoconductors that operated at room and near room temperatures with the close to the theoretical value detectivity.

Photoelectric memory in GaAs/AlGaAs quantum well infrared photodetectors

GaAs/AlxGa1-xAs quantum well infrared photodetectors grown by molecular-beam epitaxy with x varied from 0.26 up to 0.43 are investigated. The huge increase of dark current (by 2 - 3 orders) in photodetectors with x approximately equals 0.4 after illumination of samples by optical radiation ((lambda) < 1.3 micrometers ) at lowered temperatures and the subsequent slow dark current relaxation are observed. The model of barriers with a local sag potential increasing tunnel current is proposed. The value of the sag potential is increased at optical ionization of unintentional deep levels in the barrier and is decreased at the subsequent capture of electrons from conduction band on deep levels. Analysis of the dark current kinetics allowed to determine some parameters of these deep levels.

Selective photodetectors: a view from Russia

A brief review is given of the problems one may be faced with in developing selective multicomponent photodetectors for a wide wavelength range of electromagnetic radiation-from approximately 0.1 μm in the ultraviolet to 50 μm in the infrared spectrum regions. The limits of this range are mainly defined by spectral distribution of brightness of the solar direct or scattered radiation and by the spectrum of thermal radiation of the earth and objects on its surface.

LWIR detectors for subthermonuclear plasma study

We developed high-frequency (HF) photodiodes (PD) and photoconductors (PC) operated in spectral range 1-20 mum and frequencies over 1 GHz on the basis of HgCdTe heteroepitaxial structures (HS) with special composition distribution throughout the thickness grown on ZnCdTe/GaAs substrates by molecular beam epitaxy (MBE). The measurement HF PD and PC parameters were carried out. HF PD were used for study of subthermonuclear plasma.

Fabrication and characteristics of long-wavelength infrared planar photodiodes on molecular beam epitaxial p-HgCdTe films

The results of MBE growth of CdHgTe epilayers and fabrication of photosensitive in 8 - 10 mkm region small p-n junctions using planar technology are presented. During MBE epitaxy the growing dynamic, composition and surface roughness were controlled in situ using build in high energy electron diffractometer and ellipsometer. Small area photosensitive diodes (50 X 70 mkm) were fabricated using planar technology and annealing under anodic oxide film. The measurements of V-I, spectral response and noise characteristics showed that the photodiodes on MCT epilayers grown by MBE have an acceptable parameters for fabrication of the linear and 2D photodiode arrays.

Selective photodetectors: a view from the USSR

The present report gives a brief review of the problems one may be faced with in developing selective multicomponent photodetectors for rather a wide wavelength range of electromagnetic radiation--approximately from 0.1 micrometers in the ultraviolet to 50 micrometers in the infrared (IR) spectrum regions. The limits of this range are mainly defined by spectral distribution of brightness of the solar direct or scattered radiation and by the spectrum of thermal radiation of the Earth and objects on its surface.