Photoelectrical properties of Cd_xHg_1-xTe epitaxial layers irradiated by nanosecond laser pulses

Abstract

Cd,Hg,_,Te epitaxial layers ( x = 0.28) with cellular structure are studied. The influence of laser pulses of nanosecond duration over a wide energy range on the photoelectrical and electrophysical properties of Cd,Hgl-,Te epitaxial layers is investigated. Laser pulses above the material melting threshold cause the formation of a subsurface layer with a wider forbidden gap. This is connected with residual stress and with the change of composition in the subsurface layer. It has been shown that increasing photoconductivity of the studied layers is connected with the gettering properties of the regions of small disorientation towards the electrically active point defects.

Role of laser-induced stress and shock waves in modification of the photoconductivity of films

“…Irradiation of the CMT films obtained with laser pulses of energy densities up to J = 0.64 J cm −2 increased the photoconductivity signal in both variants of illumination of the samples (figure 2, curve 1, and figure 3(a), curves 2 and 3). It had been established that the photosensitization of CMT films with a cellular structure was due to a reduction in the effective density of electrons by more than an order of magnitude and an increase in their mobility [3]. In order to identify the mechanism of laser action on epitaxial CMT films, we also used the copper-foil-coated samples, which were subjected to irradiation as well.…”

“…Irradiation of semiconductors with nanosecond laser pulses of quantum energy hν > E g , which are absorbed by thin surface layer, alters the electrophysical properties of the crystals because of modification of their defect structure [1][2][3][4][5][6]. Changes in these properties are attributed to heating, electron and phonon excitation, and generation of the acoustic and shock waves [1,2].…”

“…Changes in these properties are attributed to heating, electron and phonon excitation, and generation of the acoustic and shock waves [1,2]. Probably the last of these factors plays the greatest role in the case of pulsed laser activation of a material in layers of thickness considerably greater than the depth of laser radiation absorption [2][3][4][5][6]. This condition is frequently realized under laser treatment of narrow bandgap semiconductors such as the Cd x Hg 1−x Te (CMT) solid solutions [2][3][4].…”

“…Probably the last of these factors plays the greatest role in the case of pulsed laser activation of a material in layers of thickness considerably greater than the depth of laser radiation absorption [2][3][4][5][6]. This condition is frequently realized under laser treatment of narrow bandgap semiconductors such as the Cd x Hg 1−x Te (CMT) solid solutions [2][3][4]. This semiconductor is the basic material for infrared photoelectronics [7][8][9][10].…”

“…The goal of this work is to study the role of the stress and shock waves in laser-stimulated photosensitization of epitaxial n-type CMT films with a cellular structure † E-mail address: gnatyuk@class.semicond.kiev.ua that had been established by us earlier [3]. Although the phenomenon discovered of an increase in the photoconductivity signal offers a fertile field for the design of infrared detectors based on the CMT films, the question of change in the properties of deep-seated layers of laserirradiated samples is still open.…”