IDEA #55R09Z Time Dependent Piezophotoresistive Effect And Evaluation Of Its Usage In Electronics

SCIENTIFIC INNOVATIVE PROJECTS FROM MINISTRY OF EDUCATION AND SCIENCE AND NATIONAL ACADEMY OF SCIENCES OF UKRAINE Fig. 1. Spectra of Piezophotoconductivity TIME DEPENDENT PIEZOPHOTORESISTIVE EFFECT AND EVALUATION OF ITS USAGE IN ELECTRONICS Description: Piezophotoconductivity (PPC) appears as a result of the mutual light and mechanical pressure action. Their mutu(cid:28) al influence on the electron system of a semiconductor appears as the electroconductivityconstituent proportion(cid:28) al 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(cid:28)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 repre(cid:28) sent 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(cid:28)given results and consid(cid:28) ering their reproduction in In4Se3 crystals [3], two typi(cid:28) cal peculiarities of time(cid:28)dependent PPC should be marked: oscillative character and spectral dependence of phase shift. Mechanical pressure in the crystal causes to the ener(cid:28) gy redistribution over electron states in bands. It is the main reason for the time(cid:28)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 nonsta(cid:28) tionary PPC spectra formation which consists of the mod(cid:28) ulation of the energy dependence of combined density of states by mechanical pressure. The direct modulator factor is the U(cid:28)process of electron dissipation caused by mechan(cid:28) ical 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 cen(cid:28) ters within the energy structure of a semiconductor can be experimentally found by the methods of modulation spec(cid:28) troscopy. Innovative Aspect and Main Advantages: New method of the electron states studying; new genera(cid:28) tion of the detectors of acoustooptical signals. Areas of Application: Acoustoelectronics, detectors of combined acousto(cid:28)optical signals, computer technique and qubite 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(cid:28)032(cid:28)261(cid:28)14(cid:28)90 Fax: 8(cid:28)032(cid:28)261(cid:28)14(cid:28)90 Email: stakhira@ekectronics.wups.lviv 96 SCIENCE AND INNOVATION. Special Issue, 2007