Magnetoluminescence investigations of Si/Si0.76Ge0.24 quantum wells

Photoluminescence experiments in high magnetic fields reveal diamagnetic sh ifts consistent with a type-II conduction band offset of about 55 meV for S i/Sio(0.76)Ge(0.24). We point out that for such a type-II offset a magnetic field induced changeover from Delta(2)- to Delta(4)-like recombination is expected for an 8.5 nm wide quantum well, and that: this changeover can exp lain our measurements on this well at low excitation power. The magnetolumi nescence data provide evidence for localized and free exciton recombination s, which are hardly separable without the magnetic field. For interpretatio n of the data we employ calculations within an effective-mass model, obtain ing two-particle ground-state wave functions for excitons in quantum wells at high magnetic fields.