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

Abstract

An influence of laser-induced stress and shock waves on photoelectric properties of epitaxial n-Cd 0.28 Hg 0.72 Te (CMT) films with a cellular structure was studied. Irradiation of CMT films with nanosecond ruby laser pulses resulted in a modification of photoconductivity spectra and an increase in the photosensitivity because of segregation of electrically active point defects at the cell boundaries (acting as sinks) and also because of changes in their electron states as a result of action of the laser-generated stress and shock waves. Using the calculations of the temperature of the samples, the depth of shock wave formation and the amplitude of shock wave at laser irradiation, it was established that the strongest photosensitization of CMT took place in deep-seated layers where the shock wave was formed. This deduction was confirmed by an increase in the photosensitivity of purpose-designed samples coated with copper foil in such a way as to exclude the photo-and thermal effects under laser irradiation of CMT solid solutions.

Analysis of the possibility to control complex semiconductors properties by shock wave treatment

“…Protection of samples from the direct laser irradiation makes the principal difference between our study and [3]. As a heat wave penetrates into a sample at several µm in the SW generation mode, this heat impact can cause the solid solution to dissociate, mercury to diffuse and other heat phenomena to happen in HgCdTe.…”

Influence of surface stress and atomic defect generation on Rayleigh waves in laser-excited solids

“…When a solid is illuminated with a laser pulse, absorption of the laser pulse results in a localized temperature increase, which in turn causes lattice defects, and generates a elastic -concentration wave in the solid. Various structural imperfections in the crystal lattice, i.e., atomic point defects, which are produced from the lattice site atoms due to pulsed laser beam introduce a significant strain of the medium as a result of the difference between the radii of lattice atoms and defects [9], and play an important role in surface modification of solids exposed to laser radiation [10][11][12][13]. The formation of defects may occur also in the laser fast recrystallization and laser annealing, and laser-assisted thin-film deposition processes.…”

Modification of photoelectric and electrical properties of III-V semiconductors by pulsed laser irradiation

“…One of the most important problems in the manufacture of modern electronic devices lies in a modification of the state and properties of the semiconductor surface, as for instance it is in removal of oxide films, stress relieving, local surface annealing, forming the surface regions enriched or depleted with majority carriers, etc. Based upon advantageous use of laser procedure to attain these ends, as applied to II-VI compounds [1][2][3], it is of appropriate to study the possibilities of cleaning a surface of III-V semiconductors and modifying their properties by irradiation with nanosecond laser pulses. The application of short laser pulses with light that is strongly absorbed only by thin (of the order of the laser absorption depth) surface layer has excluded the photo-and thermal influence on the bulk of crystals.…”