Papers by Author: Antonio Castaldini

Abstract: This paper reports on the defects created in a 6H-SiC p-type substrate by a process of ion implantation and a quite low temperature annealing (1300 °C), suitable for the realization of the source/drain regions of a MOSFET because it does not give rise to step bunching phenomena. Current voltage measurements showed the presence of a group of diodes featured by excess current. The effects of defects under the implanted layer on the transport properties of the diodes were investigated by DLTS: four hole traps were detected in all the measured diodes; besides, a broadened peak around 550 K was detected in the diodes that show excess current.

Abstract: High performance SiC detectors for ionising radiation have been designed, manufactured and tested. Schottky junctions on low-doped epitaxial 4H-SiC with leakage current densities of few pA/cm2 at room temperature has been realised at this purpose. The epitaxial layer has been characterised at different dose of radiations in order to investigate the SiC radiation hardness. The response of the detectors to alpha and beta particle and to soft X-ray have been measured. High energy resolution and full charge collection efficiency have been successfully demonstrated.

Abstract: We report on the investigation of electrical properties of polycrystalline 3C-SiC thin films deposited on oxidized Si by low pressure chemical vapor deposition (LPCVD) to obtain bi-layer structures [Si(100)/SiO2/poly 3C-SiC] for pressure sensors and micro-electromechanical system (MEMS) applications. Polycrystalline 3C-SiC films have been preliminary characterized in their compositional, structural, morphological and electrical properties. Moreover, metal contact definition has been carefully optimized by transmission line method (TLM) analyses performed at different temperatures. We focuses the attention on the evaluation of the bulk resistivity (ρ), the specific contact resistivity (ρc) and their behavior dependence on the temperature because these are the characteristics of major importance for the fabrication of pressure sensors or MEMS.

Abstract: n+/p diodes have been realized by 300°C phosphorus ion implantation and subsequent annealing at 1300°C. An electrical characterization of the devices as well as a study of the defects introduced by the implantation process has been made. I-V measurements pointed out that the diodes maintain a good rectifying behavior up to 737K. DLTS analyses detected the presence of three traps, T2, T3 and T4, which are not due to the implantation process, and a high energy trap, T5, that could be related to the surface states at the Ni/SiC interface.

Abstract: The effects of irradiation with protons and electrons on 4H-silicon carbide epilayers were investigated. The particle energy was 6.5 and 8.2 MeV. The electronic levels associated with the irradiation-induced defects were analyzed by current-voltage characteristics and deep level transient spectroscopy measurements up to 700 K. In the same temperature range the apparent free carrier concentration was measured by capacitance-voltage characteristics to monitor possible compensation effects due to the deep level associated to the induced defects. Introduction rate, enthalpy and capture cross-section of such deep levels were compared and some conclusions about the nature of the defects were drawn.