Gap states at cleaved InSb(110) surfaces

Abstract

The electronic properties of cleaved InSb(110) surfaces of p-type bulk material are investigated at low temperatures by measurements of integral and differential field effect. The asymmetry in the voltage dependence of the field induced changes of surface conductivity implies depletion layers in the surface depending on the cleavage state. Annealing to temperatures less than 350°C results in weak accumulation layers independently of the cleavage state. The analysis of the experimental results provides the term spectra of surface states within the energy gap. The general shape of the surface state density per energy interval shows a continuous distribution with a minimum near the middle of the gap and increasing tails towards the band edges. Near the conduction band minimum a peaking structure is superposed to the continuous distribution depending on the cleavage state. The nature of the spectrum of surface states within the gap is discussed on the base of intrinsic and extrinsic states.