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Home Material Sciences Time dependent piezophotoresistive effect and evaluation of its usage in electronics

Time dependent piezophotoresistive effect and evaluation of its usage in electronics


Piezophotoconductivity (PPC) appears as a result of the mutual light and mechanical pressure action. Their mutual influence on the electron system of a semiconductor appears as the electroconductivityconstituent proportional to the product of light and mechanical pressure which vary according to the harmonic law. Using the method of phase detection PPC can be easily separated from the other constituents of electroconductivity.

The goal of this paper is to develop the mechanism of formation of PPC spectra including their dynamics; the conditionality of PPC spectra structure by the law of band dispersion; to evaluate the role of U-processes in spectra formation. Experimental results are given for the layer structure А3В6 crystals. PPC spectrum can be considered as the system of bands the spectral position of which corresponds to the fundamental absorption. The instability in the band maximums (maximum is corresponded to the PPC increase) was observed in some cases. These bands represent the set of narrow lines of particular high intensity.

The peculiarity of the dynamics of PPC spectra is phase displacement of PPC in respect to the phase of modulated mechanical pressure on the angle value φ, which depends on the energy of light quantum (it can reach the value π/2). By summing up the above given results and considering their reproduction in In4Se3 crystals [3], two typical peculiarities of time-dependent PPC should be marked: oscillative character and spectral dependence of phase shift.

Mechanical pressure in the crystal causes to the energy redistribution over electron states in bands. It is the main reason for the time-dependent combined density of states. In respect to this the absorption factor consists of two components:
the first one is proportional to combined density of states, and
the second is proportional to the speed of its change.

We propose the mechanism of nonstationary PPC spectra formation which consists of the modulation of the energy dependence of combined density of states by mechanical pressure. The direct modulator factor is the U-process of electron dissipation caused by mechanical pressure.

The mutual action of light and varying pressure causes the appearance of discrete resonance centers which while absorbing light promote a sharp increase of concentration of nonequillibrium of charge carriers for the corresponding light quantum energies. The energy position of these centers within the energy structure of a semiconductor can be experimentally found by the methods of modulation spectroscopy.

Innovative Aspect and Main Advantages

New method of the electron states studying; new generation of the detectors of acoustooptical signals.

Areas of Application

Acoustoelectronics, detectors of combined acousto-optical signals, computer technique and qubite

Spectra of Piezophotoconductivity
Fig. 1 Spectra of Piezophotoconductivity

Stage of Development

Development phase – laboratory tested

Contact Details

Ivan Franko Lviv National University
Profesor Stakhira Yosyp Mykhajlovych
Address: vul. Dragomanova, 50, Lviv, 79005, Ukraine
Telephone: 8-0322 61-1490
Fax: 8-0322 61-1490
Email: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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