Changes in the surface potential of InSb shift some structure in its electroreflectance spectrum to larger, and other structure to smaller, photon energies. Some structure is virtually unaffected. These shifts can consistently be explained by variations in the conduction-band population caused by changing the separation between the Fermi level and the conduction-band edge. The results establish band-population effects as an additional modulation mechanism in electroreflectance and permit the classification of electronic transitions into three categories: Structure displaying red, blue, or no shift correlates with electronic transitions starting from, ending at, or bridging the Fermi level. The effect permits optical monitoring of the surface potential.

• Received 26 May 1969

DOI:https://doi.org/10.1103/PhysRev.187.1021