Interplay of excitonic radiative recombination and ionization in photocurrent spectra of thick barrier GaAs/AlAs multiple quantum wells

We have studied photocurrent (PC) spectroscopic features of a relatively th ick barrier GaAs/AlAs multiple quantum well p-i-n diode at 18K, It is found that the PC spectra do not reflect the photoabsorption spectral lineshape under the low field condition and show negative PC peaks at the exciton res onance wavelengths where the absorption coefficient is maximum. These PC di ps are qualitatively explained by considering the distribution of photogene rated carriers and competition between the carrier transport and recombinat ion. A tunneling model calculation is carried out to successfully explain t he PC spectral features as well as the field dependence of PC intensity by taking into account the photogenerated carrier distribution and the exciton ic absorption lineshape variations with the field.