Semimetal to semiconductor transition in ErP islands grown on InP(001) dueto quantum-size effects

Thickness-dependent changes in the electronic states of semimetal ErP islan ds grown on the InP(001) surface by organometallic vapor-phase epitaxy have been investigated by means of scanning tunneling microscopy/spectroscopy. The normalized differential conductance spectra show a semimetal behavior f or the ErP islands (20-50 nm in size) with thickness larger than 3.4 nm, wh ile the spectra taken for the islands thinner than 3.4 nm reveal a semicond ucting gap varying to similar to 1 eV. The thickness dependence of the obse rved gap is explained by the energy gap between the electron sublevel and t he hole sublevel calculated using a one-dimensional square-well potential m odel with infinite barriers. The results demonstrate a semimetal to semicon ductor transition due to the quantum size effect on the semimetal ErP band structure with a band overlap of -0.3 eV. [S0163-1829(99)01020-6].