| This work uses density functional theory within the local density approximation (LDA) and the generalized gradient approximation to investigate the electronic and structural properties of group III-V compounds under conditions of strain and compression, with primary emphasis on the III-V nitrides. The III-V nitrides are of particular importance in semiconductor devices because of their wide band gaps, large piezoelectric response, and spontaneous polarization allowed by the wurtzite structure. Polarization induced bound charge arising from differences between opposite sides of a III-V nitride heterojunction is also useful in creating quasi-two dimensional electron gases with large carrier concentrations.; All of the III-V nitrides, including BN and TlN, are examined in this work, with a prediction for the lattice constants of TlN in wurtzite. In Chapter 2, local densities of state for Al0.25Ga0.75N and InN are determined and agree well with experimental measurements from electron energy loss spectra. The behavior of the structure parameters of all III-V nitrides in the wurtzite structure under biaxial and uniaxial compression are determined in Chapter 3, along with various elastic constants and moduli. Using the Berry Phase concept, the spontaneous polarization and the piezoelectric polarization arising from biaxial strain are determined for all III-V nitrides in the wurtzite structure in Chapter 4. Calculation of the spontaneous polarization of selected III-V ternary nitride alloys then allows determination of the bound charge induced by polarization differences at AlxGa 1−xN/GaN and InxT 1−xN/TlN interfaces. Finally, in Chapter 5 a systematic study of all III-V compounds under hydrostatic compression is undertaken, and calculated enthalpies are used to determine transition pressures between structural phases, with a possible stable phase of sc16 predicted in the boron III-V compounds other than BN. |
