In this work we report on the characteristics of (Ni/Au)/AlGaN/GaN/SiC Schottky barrier diode (SBD). A variety of electrical techniques such as capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS) measurements were used to characterize the diodes. We observed an hysteresis phenomenon on the C-V characteristics in the Schottky diode. The parasitic effect can be attributed to the presence of traps in the heterostructure. Deep defects analysis was performed by deep-level transient spectroscopy (DLTS). One hole trap have been detected with an activation energy and a capture cross-section of 0.75 eV and 1.093 × 10−11 cm2. The localization and the identification of this trap have occurred and a correlation between the defect and the hysteresis phenomenon has been discussed. At high temperatures, the DLTS signal sometimes becomes negative, likely due to an artificial surface-state effect.

AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O3) substrates reveal anomalies like kink effect, current collapse, hysteresis phenomena on I ds -V ds and I ds -V gs . These parasitic effects can be attributed to the presence of traps in the hetero-structure. Deep defects analysis was performed by conductance deep level transient spectroscopy (CDLTS) under drain pulse. Four electron traps have been detected with activation energy and capture cross-section of 2.62 eV, 1.18 eV, 0.97 eV, 0.48 eV, σ n = 2.4 × 10-17 cm2 and σ n = 2.37 × 10-14 cm2, σ n = 2 × 10-12 cm2 and σ n = 4.67 × 10-14 cm2 respectively. The localisation and the identification of these traps have occurred and a correlation between defects and parasitic effects has been discussed.

1.3 $\mu $ m room temperature emitting multiple-stacked InAs/GaAs(001) quantum dots (QDs) are grown by molecular beam epitaxy (MBE) and investigated by photoluminescence (PL), polarized photoluminescence (PPL), photoluminescence excitation (PLE), time resolved photoluminescence (TRPL) and atomic force microscopy AFM. The PL measurement shows that two distinct sets of QDs coexist in the sample. The AFM image of the tenth QDs layer not only confirms the bimodal size distribution of the QDs but also shows that the large QDs are elongated along the [1-10] direction. The former structural information has been verified by PPL. Through the excitation density dependent PL and the detection energy dependent PLE we have evidenced two kinds of QDs within the small size dots population: isolated QDs and laterally coupled QDs with vertically coupled large size QDs. The large size dot population is found to possess a long PL decay time confirming that they are electronically coupled. In the meanwhile the PL decay time of the small QDs is found to be similar to that of single layer QDs. These results would help improve understanding some fundamental properties of an interesting structure for optoelectronic applications.

In this paper, we report the theoretical predictions of a high-index GaAs substrate ((111)A and (311)A) on the subband structure and thereafter on the 2D electron density of Si δ-doped Al0.33Ga0.67As/In0.15Ga0.85As/GaAs pseudomorphic high electron mobility transistor (pHEMT) with an additional Inx Ga1-x As (x > 0.15) thin layer embedded in the channel. We have seen that the electronic structures and the electron density are quite sensitive to the additional Inx Ga1-x As (x > 0.15) layer thickness, indium composition and to their position in the channel. An optimal position of the additional Inx Ga1-x As layer was found to be corresponding to the maximum of the first eigen envelope function for the different growth directions. We report that the optimised electron density is obtained in the structure grown on (111)A GaAs substrate. In this case the electron transfer is significantly higher than those grown on (311)A and (001) GaAs substrates respectively.

Admittance spectroscopy has been performed on Al dots deposited on porous Silicon grown on p+ substrates. They exhibit d.c. current-voltage characteristics of a metal-insulator-semiconductor structure containing a large concentration of localized states in the insulator. The admittance is composed of a frequency (ω) independent conductance while the reactance varies as ω s with s = 1. This strongly suggests that conduction through porous Silicon layers is governed by hopping between surface states.

Time resolved photoluminescence (PL) measurements are performed on oxidized and fresh porous silicon at room temperature. Comparing the evolution of the nanosecond time delayed PL in both cases, a new feature of the PL spectra is identified: the fast-red band, present as well in fresh or aged samples. The nonlinear excitation intensity dependence of this component is described by a simple model where, the Auger effect inside isolated silicon nanocrystallites plays the dominant role.

We present the temperature and frequency dependence of the current-voltage (I-V) characteristics of Al barriers deposited on porous Si grown on p-type Si substrates. These barriers exhibit a rectifying behaviour when the temperature is higher than 250 K. The I-V characteristics can be understood by a conduction in porous Si taking place via free electrons thermally excited from Pb centers associated with the existence of a SiO2-Si interface and via hopping between these Pb centers.

The effects of high temperature isothermal annealing on the electrical properties of donor and acceptor defects in n-type LEC GaAs are investigated. The annealing experiments are performed under As-rich atmosphere at 1000°C for 1–4 and 16 hours followed by a very quick quenching into cold water of the quartz ampoules containing the samples. The donor and acceptor levels are detected respectively by standard (DLTS) and optical (ODLTS) deep level spectroscopy. DLTS results show the presence of one single donor level present in unannealed and annealed samples at Ec - 0.79eV which is identified as the well known electron trap EL2 Only the sample annealed for 16 hs exhibits the presence of a new electron trap named TAI at Ec - 0.32eV. The appearance of TAI is correlated in one hand with the evolution of EL2 concentration and in the other hand to the effect of long duration (16 hs) of the treatment. For acceptor levels, two hole traps HT1 and HT2 are detected respectively at EV + 0.18 eV and EV+ 0.28 eV. HT1 is detected only in samples annealed for 4 and 16 hs and HT2 is detected in all studied samples. Photoluminescence (PL) measurements show the presence of the 1.44 eV band corresponding to gallium antisite GaAs defect. This band observed in unannealed and annealed samples shows that GaAs remains stable even after thermal annealing at lOOO°C for 16 hs and it is correlated with the presence of HT2.

Combined photoluminescence and DLTS investigations of semi-insulating and n-type GaAs before and after a 15min, 850°C heat treatment under AsH3 reveal that the treatment which anneals the EL6 center leads also to a disappearence of the O.8eV PL band. The suggested correlation between EL6 and the O.8eV PL is confirmed by the determination of the electron capture barrier of EL6 and the Franck-Condon shift deduced from the temperature dependence of the PL band leading to a consistant Configuration Coordinate diagram of this defect.

We present data which show that electron emission from the DX center is sensitive to the Poole-Frenkel effect. We demonstrate that this result implies that the DX center is an L effective-mass state of the donor impurity accompanied by a small lattice relaxation. We show that all the observations so far obtained on this center are in agreement with this model.