Band-tail Formation and Band-gap Narrowing Driven by Polar Optical Phonons and Charged Impurities in Atomically Resolved III-V Semiconductors and Nanodevices

High-doping-induced Urbach tails and band-gap narrowing play a significant role in determining the performance of tunneling devices and optoelectronic devices such as tunnel field-effect transistors, Esaki diodes, and light-emitting diodes. In this work, Urbach tails and band-gap-narrowing values are calculated explicitly for GaAs, InAs, GaSb, and GaN as well as for ultrathin bodies and nanowires of the same materials. Electrons are solved for by the nonequilibrium Green's function method in multiband atomistic tight binding. Scattering on polar optical phonons and charged impurities is solved for in the self-consistent Born approximation. The corresponding nonlocal scattering self-energies and numerically efficient formulations for them are introduced for ultrathin bodies and nanowires. The predicted Urbach band tails and conduction-band-gap narrowing agree well with the experimental literature for a range of temperatures and doping concentrations. Polynomial fits of the Urbach tail and band-gap narrowing as a function of doping are tabulated for quick reference.