IMPACT IONIZATION AND LIGHT-EMISSION IN GAAS METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS

A study of light emission from GaAs metal‐semiconductor field effect transistors and its connection with impact ionization phenomena is presented. First, the electrical behavior of the device in the preavalanche regime is characterized by measuring the excess gate current. Numerical simulations are performed, showing that the excess gate current is due to the collection of impact‐ionization‐generated holes at the gate electrode. Then, the energy distribution of the emitted photons in the range 1.5–3.1 eV is analyzed. The integrated intensity of photons emitted with energy above 1.5 eV is shown to be proportional, for large negative gate biases, to the product of gate and drain currents, suggesting direct recombination of channel hot electrons with impact‐ionization‐generated holes as the dominant emission mechanism. The deviation from simple proportionality at gate voltages around 0 V indicates that in implanted devices in open channel conditions other mechanisms, such as bremsstrahlung, may significantly contribute to the intensity of the emitted light.