NEGATIVE DIFFERENTIAL GAP RENORMALIZATION IN TYPE-II SUPERLATTICES

A quantitative determination of the band gap renormalization in type-I I GaAs/AlAs superlattices under high excitation is reported. The time- resolved photoluminescence after intense picosecond excitation is anal yzed using a detailed luminescence lineshape fit. The renormalization of the type-I transition is found to be comparable to that in type-I s uperlattices, whereas the type-II transition reveals a negative differ ential renormalization. This is attributed by a quantitative calculati on to the space-charge effects caused by the carrier separation.