In this work we report on the characteristics of a (Ni/Au)/AlGaN/GaN/SiC Schottky barrier diode (SBD). A variety of electrical techniques, such as gate current-voltage (I-V), capacitance-voltage (C-V), and deep level transient spectroscopy (DLTS) measurements have been used to characterize the diode. The behavior study of the series resistance, RS, the ideality factor, n, the effective barrier height, Φb, and the leakage current with the temperature have emphasized an inhomogeneity of the barrier height and a tunneling mechanism assisted by traps in the SBD. Hence, C-V measurements successively sweeping up and down the voltage have demonstrate a hysteresis phenomenon which is more pronounced in the temperature range of 240 to 320 K, with a maximum at ∼300 K. This parasitic effect can be attributed to the presence of traps activated at the same range of temperature in the SBD. Using the DLTS technique, we have detected one hole trap having an activation energy and a capture cross-section of 0.75 eV and 1.09 × 10−13cm2, respectively, seems to be responsible for the appearance of the hysteresis phenomenon.

Optical properties of Nd3+ -doped phosphate glasses have been studied on the basis of the Judd-Ofelt theory. With the intermediate cross-section value and the weak 4 / 6 parameter, we expect a relatively prominent 4 F3/2 4 I11/2 laser emission. The quenching effect of the emission intensity is discussed in terms of cross-relaxation between the Nd3+ ions as well as energy transfer processes within the host matrix. From the investigation of the decay rate from the 4 F3/2 state with the neodymium concentration, we suggest that self-quenching is insured by dipole-dipole interaction. This result was also confirmed by the simulation of the decay with the Inokuti-Hyrayama model.

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In order to investigate the optical properties of wurtzite (Wz) InP nanowires grown on Si(001) by solid source molecular beam epitaxy with the vapour-liquid-solid method, the growth temperature and V/III pressure ratio have been optimized to remove any zinc-blende insertion. These pure Wz InP nanowires have been investigated by photoluminescence (PL), time-resolved PL and PL excitation. Direct observation of the second and third valence band in Wz InP nanowires using PL spectroscopy at high excitation power have been reported and, from these measurements, a crystal field splitting of 74 meV and a spin-orbit interaction energy of 145 meV were extracted. Based on the study of temperature-dependent optical properties, we have performed an investigation of the thermal escape processes of carriers and the electron-phonon coupling strength.

Optical absorption and photoluminescence properties of Er3+-doped 70TeO2-30ZnO glass are investigated. Judd-Ofelt intensity parameters of Er3+ have been determined to calculate the radiative transition probabilities and the radiative lifetimes of excited states. An infrared to visible up-conversion was observed at room temperature in this tellurite glass system using a 797 nm excitation line. A study of the 4S3/2-4I15/2 transition (554 nm) versus power excitation provided evidence for a two-step up-conversion process under this excitation. A red emission (663 nm) originating from the 4F9/2-4I15/2 transition has been observed as well. It was found that the efficiency of this up-conversion line is enhanced considerably with the Er3+ concentration relative to the green emission (554 nm). This behaviour has been explained in terms of an energy transfer between excited ions. The temperature dependence of up-conversion intensity has been also studied in the range 40-310 K. It was found that the thermal quenching of the green emission (4S3/2-4I15/2) is large enough compared with those of the red transition (4F9/2-4I15/2 ). This thermal quenching has been discussed using the Riseberg and Moos model of multiphonon emission. It has been shown that the latter approach is not consistent with existing results. A complete analysis of the temperature-dependent up-conversion has been made using an additional decay rate which may be attributed to a non-radiative energy transfer and/or a charge transfer through trapping impurities. A good agreement has been achieved between measured and computed data.