Temperature dependent Band gap Correction model using tight-binding
approach for UTB device simulations
Ultra-thin body (UTB) devices are being used in many electronic
applications operating over a wide range of temperatures. The
electrostatics of these devices depends on the band structure of the
channel material, which varies with temperature as well as channel
thickness. The semi-empirical tight binding (TB) approach is widely used
for calculating channel thickness dependent band structure of any
material, at a particular temperature, where TB parameters are defined.
For elementary semiconductors like Si, Ge and compound semiconductors
like GaAs, these TB parameters are generally defined at only 0 K and 300
K. This limits the ability of the TB approach to simulate the
electrostatics of these devices at any other intermediate temperatures.
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 (for which TB
parameters are available), and show that the band curvature at the band
minima has minor variation with temperature, whereas the change of band
gap significantly 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 TB parameters
defined at 0 K, along with a suitable channel thickness and temperature
dependent band gap correction.