Papers by Author: Sebania Libertino

Abstract: The defects formation in ion-irradiated 4H-SiC was investigated and correlated with the electrical properties of Schottky diodes. The diodes were irradiated with 1 MeV Si+-ions, at fluences ranging between 1×109cm-2 and 1.8×1013cm-2. After irradiation, the current-voltage characteristics of the diodes showed an increase of the leakage current with increasing ion fluence. The reverse I-V characteristics of the irradiated diodes monitored as a function of the temperature showed an Arrhenius dependence of the leakage, with an activation energy of 0.64 eV. Deep level transient spectroscopy (DLTS) allowed to demonstrate that the Z1/Z2 center of 4H-SiC is the dominant defect in the increase of the leakage current in the irradiated material.

Abstract: In this paper, some basic aspects related to defects and SiC devices performances are discussed. Our recent work is reviewed and inserted in the international research scenario. In particular, some issues relative to rectifying metal/SiC contacts will be treated in more detail. In fact, establishing a correlation between material defects, processing induced defects and irradiation induced defects with the electrical behaviour of Schottky contacts is extremely important for the future optimization of almost all electronic devices, sensors and particle detectors.

Abstract: The effects of ion irradiation on the Ti/4H-SiC Schottky barrier are discussed. The Ti/SiC interfacial region of test Schottky diodes was irradiated with 8 MeV Si+4 ions at fluences between 1×109 and 1×1012 ions/cm2. By increasing ion fluence, an increase of the Schottky barrier FB was observed, from FB=1.05 eV in the non-irradiated sample to FB =1.21 eV after irradiation at the highest fluence, accompanied by a decrease of the leakage current. Using different experimental analytical techniques enabled us to correlate the modification of the interfacial region with the contacts electrical behaviour. In particular, the structural and electrical modifications in the nearinterface region (different orientation of the Ti film, defects in the epilayer, dopant deactivation) were responsible for the change of the Ti barrier after irradiation.

Abstract: Deep-Level Transient Spectroscopy and room temperature photoluminescence were used to characterise a 6H-SiC epitaxial layer irradiated with 10 MeV C+ and to follow the defect annealing in the temperature range 300-1400 °C. The intensity of luminescence peak at 423 nm, related to band to band transitions, decreases after irradiation and it is slowly recovered after annealing in the temperature range 1000-1400 °C. The DLTS spectra of low temperature annealed samples show the presence of several overlapping traps, which anneal and evolve at high temperatures. After 1200 °C a main level at Ec-0.43 eV (E1/E2) is detected. The comparison between luminescence and DLTS results indicates that the defect associated with the E1/E2 level is mainly responsible for the luminescence quenching after irradiation.