Spatiotemporal PL imaging of current density filaments during impact ionization avalanche in high-purity n-GaAs

Image patterns of current density filaments formed during low-temperature impurity breakdown in high-purity n-GaAs have been investigated at 4.2 K by means of the spatiotemporal photoluminescence (PL) patterns. Under a pulsed voltage with the pulse width of w=18.0 μs and the repetition frequency of 8.0 kHz, a current density filament can be observed as a quenched PL pattern. Besides, anomalously bright PL pattern was observed along the filament boundaries. With a short pulse of w=785 ns, the bright PL pattern was formed inside the current filament. The anomalous enhancement of the PL intensity was attributed to the electron-impact formation and/or the hole-impact formation of the excitons bound to ionized donors during the impact ionization avalanche of the neutral shallow donors.