EFFECT OF WELL WIDTH VARIATION ON TYPE-I TYPE-II PHOTOLUMINESCENCE INGAAS/ALAS SINGLE QUANTUM-WELLS/

We have investigated type-I/type-II transitions in MBE-grown 20, 35, a nd 50 Angstrom GaAs/AlAs single quantum wells using photoluminescence (PL) spectroscopy. The 20 and 50 Angstrom wells show a type-I peak, wh ile the 35 Angstrom well has PL peaks corresponding to both type-I and type-II transitions. Peak assignment for the 35 Angstrom-well sample is based upon excitation intensity dependent measurements, and the str ength of the type-II transition in this sample is attributed to Gamma- X mixing. Superperiodicity has been put forth as a possible explanatio n for Gamma-X mixing effects in superlattice structures, but the obser vation of this phenomenon in a single quantum well structure suggests that superperiodicity is not required for Gamma-X mixing to occur. (C) 1997 Academic Press Limited