Temperature Dependent Band Gap Correction Model Using Tight-Binding Approach for UTB Device Simulations

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In order to accurately determine the electrostatics of Ultra-Thin-Body (UTB) devices, the semi-empirical tight-binding (TB) approach is widely used for calculating the channel thickness dependent band structure of any material at those temperatures where TB parameters are available (generally defined at 0 K and 300 K). In this work, we analyze the variation of band structure for Si, Ge, and GaAs over different channel thicknesses at 0 K and 300 K, and show that the band curvature at the band minima remains unchanged with temperature, while the band gap changes significantly and affects the channel electrostatics. Based on this finding, we propose an approach to simulate the electrostatics of UTB devices, at any temperature between 0 K and 300 K, using the band structure obtained at 0 K, along with a suitable channel thickness and temperature-dependent band gap correction. From the results obtained for the channel charge density, we show good agreement with band structure based simulation results, at 300 K, over a wide range of channel thicknesses, for Si, Ge, and GaAs, while also showing good agreement with TCAD simulation results, at a typical intermediate temperature of 150 K, thus highlighting the accuracy, simplicity and wide applicability of the proposed approach.