Low Energy Electroluminescence Spectra on InP based HEMTs at Cryogenic Temperatures

We report on a spectroscopic electroluminescence study at cryogenic temperatures of InP based high-electron-mobility-transistors (HEMT's) with ultrashort gate length. Both low energy (0.7-0.9 eV) and high energy (1.3-2.2 eV) recombination bands are observed and are related to radiative recombination of carriers created by impact ionization. At low energy, the evolution of the luminescence as a function of the bias applied to the device shows that the electroluminescence intensity depends on two parameters: the gate-drain electric field and the drain current intensities. At higher energy, the emission spectrum around 1.3 eV is interpreted in terms of detrapping of localized states. Electronic temperatures of hot carriers versus Vgs are deduced from the high energy tail of the electroluminescence spectrum.