Si-doped AlGaAs/GaAs(6Â 3Â 1)A heterostructures grown by MBE as a function of the As-pressure

The effects of doping with silicon (Si) AlGaAs layers grown by molecular beam epitaxy on GaAs (6 3 1)-oriented substrates as a function of the arsenic pressure (PAs) is presented and compared with layers grown on (1 0 0) oriented substrates. The surface texture of the AlGaAs (6 3 1) films is composed by nanogrooves, whose dimensions depend on PAs. On the contrary, the MBE growth on the (1 0 0) plane resulted on rough surfaces, without evidence of formation of terraces. Mobility and carrier density of AlGaAs:Si layers grown on substrates (6 3 1) were studied as a function of PAs. The doping type conversion from p-type to n-type as a function of the As pressure is corroborated for high index samples. All the films grown on (1 0 0) exhibited silicon n-type doping. These observations were related with the amphotericity of Si, where it acts as a donor impurity occupying Al or Ga-sites or as an acceptor when it takes an As-site, depending on the competition that the Si atoms encounters with As for any of these sites. The acceptor and donor lines close to the AlGaAs transition observed by photoluminescence spectroscopy (PL) were affected by the incorporation of Si. When increasing PAs the energy of the main PL peak is redshifted for n-type AlGaAs layers, but it is shifted back towards high energy once the conduction type conversion takes place. X-ray diffraction patterns revealed high crystalline quality for samples grown at the highest PAs.