Studies on Schottky barriers with heterojunctions for III-V and II-VI semiconductor compounds

Lattice matched Ga0.52In0.48P/GaAs heterojunctions with Al Schottky barrier have been grown using gas source molecular beam epitaxy technology. Three structures, including n-type normal structure, n-type inverted structure, and p-type structure, have been studied and discussed in this thesis. Schottky barriers and interface properties were determined by current versus voltage (I-V) and capacitance versus voltage (C-V ) measurements.;Two-dimensional interface charges were found to be positive in the two normal structures, in which the wide band gap Ga0.52In0.48 P layer is grown on top of the narrow band gap GaAs layer, while two-dimensional interface charges were found to be negative in the n-type inverted structure, in which the narrow band gap GaAs layer is grown on top of the wide band gap Ga0.52In0.48P layer. The value of conduction band offset, Delta Ec (=Ec(Ga0.52In 0.48P)-Ec(GaAs)), for the n-type normal structure was --0.07 eV, which is smaller than that of 0.10 eV for the n-type inverted structure. The valence band offset, Delta Ev (=Ev(Ga0.52In 0.48P)-Ev(GaAs)), extracted from the p-type normal structure was found to be 0.36 eV.;A new switching procedure during the interval from the GaAs growth to Ga0.52In0.48P growth was applied to the n-type normal structure to improve interface quality. The new switching procedure did reduce the interface charge density. DeltaEc for the n-type normal structure with zero interface charge density was found to be 0.2 eV, which is consistent with the results obtained from the improved interfaces reported by other researchers.;Finally we reported the I-V and C-V data of an n-n ZnSe/In0.04Ga0.96As heterojunction. A double Schottky diode model was applied to explain the experimental data for the n-n heterojunction. The negative interface charges are found at tile ZnSe/In 0.04Ga0.96As interface. The conduction band offset is found to be 0.1 eV, which is lower than that which would be expected from an extrapolation of results for ZnSe/GaAs.