Investigation of the interface of GaAs/AlGaAs heterostructures.

We report on optical electrical of GaAs/AlGaAs heterostructures prepared by molecular beam epitaxy (MBE). For fixed Ga and As fluxes the damping of the oscillations of the reflection high energy electron diffraction (RHEED) pattern is strongly dependent on substrate temperature. The minimum of the damping of the intensity oscillations has been observed at 750 degree C. The best electrical properties of high electron mobility transistors (HEMT) have been found at this substrate temperature. The maximum electron mobility was 120 000 square centimetre/Vs at 77 K for a spacer of 50 A and an electron concentration of 1 *10"12" square centimetre. For the presented quantum well (QW) structures we obtained the best results at a substrate temperature of 740 degree C. In photoluminescence we obtained a full width at half maximum (FWHM) for example for a 20 nm, 4.5 nm , 2nm and 1 nm wide QW of 0.27 meV, 1.5 meV, 5 meV and 7 meV respectively.