Abstract
A theoretical investigation of impact ionization and associated light emission in GaAs MESFETs, GaAs/AlGaAs HEMTs and HBTs is presented. Based on band structure and Monte Carlo calculations, we show that light emission by hot carriers in submicron GaAs devices can be explained by direct radiative interband transitions, both below and above the gap energy. In agreement with experimental findings, a strong correlation is found between the currents associated to minority carriers and light emission.