PHOTOEXCITED PERPENDICULAR TRANSPORT THROUGH INGAAS/INP MULTIPLE-QUANTUM-WELL P-I-N HETEROSTRUCTURES

A study of the perpendicular transport of photogenerated carriers through InGaAs/InP quantum wells grown by chemical beam epitaxy is presented and p-i-n diodes with a mesa structure containing several quantum wells within the intrinsic region have been investigated. Photocurrent spectra were obtained as a function of temperature, intensity of light and electric field. The excitonic peaks, identified by considering absorption measurements and interband transition energies, were observed up to room temperature. At low temperatures, a full bleaching of excitonic features associated with a blue shift of the long wavelength spectrum edge and a red shift (Stalk effect) of the hh-el exciton peak were observed at low and high field respectively. Capacitance and photocurrent steps detected with increasing reverse bias are explained by considering a field dependence of the escape time of photogenerated carriers in a regime of non-resonant tunnelling. Thermally activated (thermionic emission over the barrier) and thermally, assisted (phonon assisted tunnelling) processes were found to dominate the transport of photoexcited carriers at high and low temperature, respectively.