Photocurrent and intrinsic modulation speeds in P-I(MQW)-N GaAs/AlGaAs stark effect modulators

Abstract

Theoretical and experimental studies on photocurrent are presented in p-i-n GaAs/Al 0.3Ga 0.7As MQW modulators and detectors. Field dependent excitonic spectra is calculated to obtain carrier generation and recombination rates using full band mixing effects in the valence band. A tunneling formalism is used to self consistently study the electric field dependence of the electron and hole collection efficiency. At low electric fields and low temperatures the carrier collection efficiency is very poor and we show that the collected photocurrent has a sublinear dependence on the impinging light intensity. This non-linearity is not due to band filling or exciton screening effects normally observed, but arises from the high recombination rates compared to tunneling rates. At higher electric field the collection efficiency is ∼ 100% resulting in a linear response and a negative differential resistance region. Consequences of our studies on intrinsic device speeds are discussed for p-i(MQW)-n modulators based on Stark effect.