Sequential screening layers in a photoexcitedIn1−xGaxAsInPsuperlattice

We have observed an unusual sequence of ten peaks in the derivative of the reverse-bias photocurrent in an $\frac{{\mathrm{In}}_{1-x}{\mathrm{Ga}}_x\mathrm{As}}{\mathrm{InP}}$ superlattice consisting of ten wells in a $p-i-n$ configuration. We show the effect is caused by the screening of the applied field by positive charge generated successively in the wells. The positive charge is a consequence of vastly different emission rates for photogenerated electrons and holes in the wells. Capacitance measurements on a $p-n$ junction with a single quantum well demonstrate the effects of the different transport properties of the two carrier types. We use the quantum-confined Stark effect as an internal probe of the electric field distribution in the superlattice to confirm the model.