Photocurrent Noise Observed by Resonant Photoexcitation at 4.2 K in n-GaAs

Low-frequency ( f < 50 Hz) photocurrent noise caused by the breakdown of the low-temperature freeze-out of neutral shallow donors at 4.2 K has been investigated under resonant photoexcitation in n -GaAs. At the onset of the breakdown (∼4 V/cm), the photocurrent noise was selectively generated by the resonant photoexcitation at the photon energies of the ( D 0 , X ) n =1,2 lines and the ( D + , X ) line. The observed results are explained by the current-filament formation.