Using an atmospheric metal-organic chemical vapor deposition system, we passivated GaAs with AlN prior to atomic layer deposition of Al2O3. This AlN passivation incorporated nitrogen at the Al2O3/GaAs interface, improving the capacitance-voltage (C–V) characteristics of the resultant metal-oxide-semiconductor capacitors (MOSCAPs). The C–V curves of these devices showed a remarkable reduction in the frequency dispersion of the accumulation capacitance. Using the conductance method at various temperatures, we extracted the interfacial density of states (Dit). The Dit was reduced over the entire GaAs band gap. In particular, these devices exhibited Dit around the midgap of less than 4 × 1012 cm−2eV−1, showing that AlN passivation effectively reduced interfacial traps in the MOS structure.
First-principles calculations are carried out to estimate the spontaneous polarization and the energy band gap bowing in YxAlyGa1-x-yN alloys lattice-matched to GaN. The ground state properties of alloys are computed by using the pseudopotential-planewave method in conjunction with generalized gradient approximation to density functional theory. We find nonlinear behavior of the spontaneous polarization and the band gap energies in YxAlyGa1-x-yN alloys and the values depend on the atomic geometry in the unit cell, especially on that of yttrium.
The effect of Mn-doping into a GaN buffer layer grown by metal organic chemical vapor deposition (MOCVD) on the reduction in the leakage current of high-electron-mobility transistors (HEMTs) was investigated. Both the surface morphology and crystallinity maintained their quality even after heavy Mn-doping. The sheet resistance of GaN films increased with increasing amount of Mn-doping. The origin of semi-insulating GaN layer is considered to be electron scattering and the carrier compensation mechanism involving deep levels generated by the Mn impurity. When using the Mn-doped GaN buffer layer for the HEMT structure, the leakage current was reduced to five orders of magnitude lower than that without Mn-doping. Although Mn-doping is an effective technique for reducing the buffer leakage current, it is found that current collapse is emphasized when using the Mn-doped GaN buffer layer. We suggest that Mn atoms, which diffused to the GaN channel layer, induce the current collapse.
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