POSITIVE TEMPERATURE-DEPENDENCE OF THE ELECTRON-IMPACT IONIZATION COEFFICIENT IN IN0.53GA0.47AS INP HBTS/

Impact ionization is a major limiting factor to the maximum operating voltage of InGaAs-based, high-speed transistors. In this work, data on the positive temperature dependence of the electron impact ionization coefficient alpha(n) in In0.53Ga0.47?As at medium-low electric fields are reported for the first time. The increase of alpha(n) with temper ature is opposite to the behavior normally observed in most semiconduc tors. This anomalous behavior implies the onset of a positive feedback between power dissipation and avalanche generation which mag adversel y affect the power handling capability of In0.53Ga0.47As-based devices , and which should be taken into account in device thermal modeling. I n the experimental procedure, based on the measurement of the multipli cation factor M - 1 in npn In0.53Ga0.47As/InP Heterojunction Bipolar T ransistors (HBT), particular care has been taken in order to rule out possible spurious, temperature-dependent contributions to the measured multiplication current.