MAGNETIC-FIELD-INDUCED LOCALIZATION OF CARRIERS IN AL0.25GA0.75AS ALAS MULTIPLE-QUANTUM-WELL STRUCTURES/

The lowest-energy interband transitions in Al0.25Ga0.75As/AlAs quantum wells are type-II, with electrons confined in the AlAs X-valley minim a and holes in the Al0.25Ga0.75As layers. We have studied the intensit y of these transitions in magnetic fields up to 30 T, in the 2-12-K te mperature range. When the magnetic field is applied perpendicular to t he structure layers the intensity of the various luminescence features associated with the type-II interband transitions decreases by an ord er of magnitude with increasing magnetic field. The field-induced inte nsity reduction is temperature sensitive and disappears for temperatur es above 15 K. No change in the photoluminescence intensity is observe d when the magnetic field is applied in the plane of the layers. The d ecrease in the recombination intensity is attributed to magnetic-field -induced carrier localization at the interfaces.