Non Radiative Processes in Phosphorene
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Non Radiative Processes in Phosphorene 1
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Eric Tea and Celine Hin 1 Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Road, Blacksburg, VA, 24060, USA 2 Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Road, Blacksburg, VA, 24060, USA ABSTRACT Novel 2D materials with interesting properties have been synthetized and characterized recently. In particular, unlike graphene, silicene or germanene, phosphorene has attracted a lot of attention because of its intrinsic band gap. This property allows for a wide range of applications where semiconductor thin films are traditionally used (e.g. electronics, optoelectronics, thermoelectrics). For each application, the device efficiency depends on how well an electrical current is extracted from the active materials, and depends on a variety of electron scattering processes. Some of these scattering processes can considerably improve or degrade device efficiencies. In this contribution we focus on non-radiative electron-hole pair generation and recombination processes, i.e. impact ionization (charge carrier multiplication) and Auger processes (charge carrier recombination). The rate of these processes is calculated from first principles and their effects on device operation are estimated. INTRODUCTION 2D semiconductor materials exhibit tunable properties such as band gaps or electronic mobility that can outperform their bulk 3D counterparts [1]. They have already been widely used in electronic and optoelectronic devices, notably in the form of semiconductor thin films. Besides device performance, the reduced raw material quantity needed to fabricate devices is another 2D material asset. Moreover, they open new venues in terms of novel device architecture and in the growing field of flexible devices [2-3]. Phosphorene, a single layer of phosphorous atoms, is a promising new 2D material exhibiting tunable properties that has been synthetized recently by exfoliation from black phosphorous. Unlike graphene, one of most the famous 2D materials, phosphorene exhibits an intrinsic direct band gap that makes it an ideal candidate for electronic, optoelectronic and thermoelectric devices. Since then, proofs of concept for phosphorene-based devices have emerged, and the ability to form pn junctions as well as the photovoltaic effect have been reported [4-7]. In this context, it is important to gain knowledge on the different processes that can limit device efficiencies, to further drive device development. In this study, two types of limiting processes have been studied: impact ionization, and Auger recombination. On one hand, Auger recombination is known to set a cap on minority carrier lifetime. Indeed, in doped semiconductors, minority charge carriers experience shorter lifetimes than the one given by radiative recombination alone. This strongly alters the efficiency of optoelectronic devices such as LEDs and solar cells. It can, however, kill undesired minor
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