Enhanced frequency response associated with negative photoconductance in an InGaAs/InAlAs avalanche photodetector

We report an InAlAs/InGaAs avalanche photodetector with the photocurrent-voltage characteristic exhibiting a negative conductance region. The frequency response of a device exhibits the internal rf-gain effect in the avalanche region, and the gain peak occurs at progressively higher frequencies as the applied voltage increases. The pulse response experiment in the time domain characterizes the formation process of the space-charge wave signal near the threshold voltage in the avalanche region. The experimental result, displaying a multivalued bandwidth curve with respect to the current-gain, shows that the avalanche process does not limit the speed of the avalanche photodetector, in contrast to the conventional one. (C) 2003 American Institute of Physics.