Surface plasmon resonance of gold and silver nanoparticle (NP) layers is investigated by the experiment as well as simulations. Although the good agreement was found for gold NP film, a significant mismatch in the resonance energy for silver NP film was observed. The deviation was assigned to the presence of silver oxide (Ag2O) in silver NPs. As an alternative to the NP size-dependent Drude model, the analysis based on effective medium approximation for refractive index of Ag-Ag2O material system is carried out and compared with the core-shell model. Both Mie's model and numerical simulation results illustrate shift of the surface plasmon resonance due to silver NP surface oxidation.

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We report on a temperature dependent threshold voltage analysis of the AlGaN∕GaN heterostructure field-effect transistors (HFETs) and Al2O3∕AlGaN∕GaN metal-oxide-semiconductor HFETs (MOSHFETs) in order to investigate the trap effects in these devices. The threshold voltage of both types of devices decreases with increased ambient temperature up to 450°C. This indicates on donor traps to be present. The temperature induced threshold voltage shift is −1.6 and −8.5mV∕°C for the HFETs and MOSHFETs, respectively. A thermally activated energy level of ∼0.2eV is evaluated and attributed to the nitrogen vacancy in the AlGaN near surface. The trap density for the MOSHFETs is about two times higher than that for the HFETs. This might be due to the high-temperature treatment (∼600°C) of the MOSHFET structure during the gate insulator deposition.

The current-voltage characteristics of the Ni/InAlN/GaN Schottky diodes were measured at various temperatures in the range of 300–820 K. The experimental data were analyzed considering different current-transport mechanisms, such as thermionic emission, generation-recombination, tunneling and leakage currents. From the fitting of experimental data it follows that the tunneling current dominates in whole temperature range. The thermionic emission becomes comparable to the tunneling current only at highest temperatures used. The barrier height of the Ni/InAlN/GaN Schottky diodes, evaluated from the thermionic emission current, shows a slightly negative temperature coefficient and its value at 300 K is 1.47 eV. Lower barrier heights were reported before, which follow from an incorrect evaluation of measured data without separation of individual current components. The dislocation density of about 2×109 cm−2 is obtained assuming dislocation governed tunneling current mechanism.

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