Tunneling recombination in semiconductor structures with nanoscale disorder
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NDUCTOR STRUCTURES, INTERFACES, AND SURFACES
Tunneling Recombination in Semiconductor Structures with Nanoscale Disorder S. V. Bulyarskia, Yu. V. Rud’b, L. N. Vostretsovaa, A. S. Kagarmanova, and O. A. Trifonova aUlyanovsk
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State University, Ulyanovsk, 432970 Russia Physicotechnical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia e-mail: [email protected] Submitted April 15, 2008; accepted for publication September 15, 2008
Abstract—A model of generalized generation–recombination theory is proposed for semiconductors with nanoscale disorder. Application of the developed recombination model made it possible to determine the parameters characterizing localization of electronic states in semiconductors with different atomic compositions and positional ordering. It is shown that the spatial parameters of this localization are in the nanoscale range. For this reason, the main transport factor is the tunneling of the charge carrier; the electronic transitions between the allowed bands and states in the mobility gap also play an important role. On the basis of the study performed, it is concluded that only consideration of both factors yields adequate description of the electronic processes in the structures based on semiconductors with nanoscale disorder. PACS numbers: 71.20.Nr, 71.23.An, 73.50.Gp DOI: 10.1134/S1063782609040071
1. INTRODUCTION Nanoscale disorder in diamond-like semiconductors can be caused by different factors. Artificial nanoscale disorder is obtained by forming an array of quantum wells, for example, in crystals based on III–V solid solutions. This process can be initiated, for example, by irradiation or ion implantation of a semiconductor. Natural nanoscale disorder can also be due to different factors: compensation, structural damage, glass formation, high defect concentration, complex formation, etc. Disorder is accompanied by spatial localization of electronic states. As a result, to recombine, charge carriers must overcome a potential barrier; barriers overcome through tunnelling is referred to as the tunneling recombination. In this study, we show that, independent of disorder origin, the general mechanism of charge transfer in such structures are generalized generation– recombination processes [1], combining Shockley recombination [2] through traps and hopping Mott transport [3]. Recombination in spatially inhomogeneous structures was investigated in [4–8]. However, the formulas for the recombination rate were obtained in these studies for particular cases. In addition, expressions for the current–voltage (I–U) characteristics were not derived, and these characteristics were not analyzed. At the same time, the I–U portions that are related to recombination in the space-charge region (SCR) carry useful information about the properties of recombination centers [9–12], which is generally disregarded. In this study, we obtained a generalized expression for the recombination rate in structures with tunnel-coupled
regions and for the I–U c
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