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SM ISO690:2012 STAMOV, Ivan, TKACHENKO, D.. The influence of absorption dichroism in ZnP2(C5 2H) on thephotoelectric properties of surface-barrier structures. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 272. |
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Materials Science and Condensed Matter Physics Editia 7, 2014 |
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Conferința "Materials Science and Condensed Matter Physics" 7, Chișinău, Moldova, 16-19 septembrie 2014 | ||||||
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Pag. 272-272 | ||||||
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The results of the exploration of polarization characteristics of photoeffect in rectifying metal-semiconductor structures based on β–ZnP2 of the n-type conduction are presented. The photoeffect in monoclinic zinc diphosphide has been found in contacts with metals, conductive oxides, electrolyties, in n-p junctions and heterojunctions [1-3]. The peak values of photoemf generated at intensive irradiation of the structures are 0.82-0.85 V. The spectral curve of the sensitivity has strong dependence in fundamental absorption edge on the polarization of radiation. Spectra generally reflects anizotropy of the absorption edge and possess features related to transitions into the fundamental absorption region. The photocurrent maximum for excitonic transition n=1 and inflections associated with states n=4, 3, 2 of inverse hydrogenlike series are visible for case of Е||с polarization. The polarization sensitivity of photocurrent manifests in all spectral range. The ratios of photocurrents Schottky-barriers for ortogonal polarizations Е^с and Е||с, calculated using models taking into account recombination processes in space-charge region and surface recombination of nonequilibrium carriers are approximately equal: I||/I^ ≈ (1- R||)α|| W /(1- R^)α^ Lp into spectral range where α|| >> α^, (α||)2 Lp, α|| Lp/ W >> 1, (α^)2 Lp, α^ Lp / W << 1 are performed and I||/I^ ≈ α||(1- R||)/ α^ (1- R^) for the case α|| ≈ α^ and (α||)2 Lp, α|| Lp/ W >> 1, (α^)2 Lp, α^ Lp / W >>1. The α^ and α|| denote the absorption coefficients in Е^с and Е||с polarizations accordingly, Lp and W – the diffusion length of nonmajor carriers and the width of depletion region. These calculations consider the significant influence of electrical field on photocurrents [4]. The experimental dependences of I||/I^ on photon energies, α||/α^ and bias voltage are obeyed the equations. The band of maximal photoelectric pleochroism measured according to 50% level varies from 64 to 130 nm. The ratio maximum of I||/I^ shifts with change of bias voltage from 0 to -4 V. The pleochroism coefficient is closed to 100%. The photosensitivity of the structures abruptly decreases to zero at wavelengths λ > 840 - 850 nm. Inside short wavelength area (360-700 nm), the ratio I||/I^ decreases values 1.2 - 3.5 and weakly depends on radiation wavelength and on bias voltage applied to the barrier. The spectral dependence of sensitivity demonstrates the inflection inside wavelegth band 665 – 694 nm and slow growth for the band 517 – 480 nm. The detected features are an evidence of the dichroic character of optical transitions in fundamental absorption region. The curves of polarization sensitivity experience changes in the dependence on donor concentration, degree of compensation of semiconductors and barrier characteristics. |
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