Si intralayers at GaAs/AlAs and GaAs/GaAs junctions: Polar versus nonpolar interfaces

The effect of inserting thin Si intralayers at GaAs/AlAs and GaAs/GaAs interfaces has been studied by photoelectron spectroscopy (PES) using synchrotron radiation. Results from polar and nonpolar interfaces are compared by analyzing samples grown by molecular-beam epitaxy on (100) and (110) substrates, respectively. The Si intralayers were inserted by an improved delta-doping method in a concentration of 2.2X10(14) cm(-2) [about 1/3 of a (100) monolayer]. When Si is introduced at GaAs-on-AlAs interfaces, the Al(2p)-to-Ga(3d) energy distance is observed to increase for both polar and nonpolar interface orientations. The insertion of Si at GaAs/GaAs(110) homojunctions modifies the Line shape of the Ga(Sd) and As(3d) peaks, resembling the changes previously reported for the (100) orientation. The results on polar junctions previously obtained were generally interpreted as band-offset changes, which would be related according to the "interface microscopic capacitor" picture with the polar nature of the interface. The PES results hen presented are difficult to reconcile with such a model because of the similar behavior shown by polar and nonpolar interfaces. Instead,they can be understood within an "overlayer band bending" interpretation. [S0163-1829(98)01519-7].