Si and Be intralayers at GaAs/AlAs heterojunctions: Doping effects

Experimental studies that suggest the possibility to "engineer" band offset s in semiconductor heterojunctions by means of intralayers have been contro versially discussed. Here, Si and Be insertions at GaAs-on-AlAs(100) interf aces are investigated by photoelectron spectroscopy (PES) using synchrotron radiation. Our aim is to clarify the effect that band bending imposes on t he determination of interface band offsets. The Ga(3d)-to-Al(2p) core-level energy separation is found to increase upon Si insertion, and to decrease upon Be insertion. The surface Fermi level moves closer to the valence-band maximum in Si-containing samples, while it moves away in Be-containing one s. These results are consistent with the n-type and p-type doping behaviors typically exhibited by Si and Be impurities in GaAs(100). The observed cor e-level offset variations support an interpretation based on band-bending a rguments, rather than on the commonly invoked band-offset changes; A simple "overlayer-capacitor" model is proposed to illustrate the physical origin of such band-bending effects. [S0163-1829(98)08643-3].