Tunneling competition of photoexcited carriers in a system of monolithically integrated dual multiple InGaAs/AlGaAs and GaAs/AlGaAs quantum wells

Vertical transport of photoexcited carriers has been studied in a p-i-n diode whoseintrinsic layer contains two different multiple quantum wells (MQW),GaAs/Al0.15Ga0.85As (MQW1) and strained In0.15Ga0.85As/Al0.15Ga0.85As (MQW2)isolated by a thick Al0.15Ga0.85As barrier. Pseudo-negative photocurrent (PC) peaks areobserved at exciton resonance wavelengths of MQW1 located far from the n-electrodeunder low electric fields, while the normal positive excitonic peaks recover withincreasing the electric field. Moreover, the PC intensity of MQW1 as a function ofinverse electric field shows linear dependence due to Fowler-Nordheim type tunnelingwith a slope change. The observed PC intensity crossover is rigorously explained bytunneling probability calculations, because of differences in the thickness and heightof the transport limiting tunneling barriers, assuming dominance of electron tunnelingtransport for the PC responses