Si δ-doping of 〈011〉-oriented GaAs and Al _xGa_1-xAs grown by molecular-beam epitaxy

Silicon δ-doping is studied on 〈011〉-oriented GaAs and Al_xGa_1-xAs grown by molecular-beam epitaxy. Hall measurements and secondary ion mass spectrometry on as-grown and on annealed samples reveal (i) that the electrical activity is reduced for the 〈011〉-oriented samples as compared 〈001〉-oriented reference samples, (ii) that the electron mobility is lower for 〈011〉-oriented samples, and (iii) that the thermal redistribution of Si impurities is comparable for both orientations. We find a markedly different dependence of the electron mobility on the spacer thickness in selectively doped 〈011〉-oriented Al_xGa_1-xAs/GaAs heterostructures, which is explained by the reduced doping efficiency of Si in 〈011〉-oriented Al_xGa_1-xAs.