Electrical and ultraviolet characterization of 4H-SiC Schottky photodiodes

Fabrication and electrical and optical characterization of 4H-SiC Schottky UV photodetectors with nickel silicide interdigitated contacts is reported. Dark capacitance and current measurements as a function of applied voltage over the temperature range 20 °C – 120 °C are presented. The results show consistent performance among devices. Their leakage current density, at the highest investigated temperature (120 °C), is in the range of nA/cm2 at high internal electric field. Properties such as barrier height and ideality factor are also computed as a function of temperature. The responsivities of the diodes as functions of applied voltage were measured using a UV spectrophotometer in the wavelength range 200 nm - 380 nm and compared with theoretically calculated values. The devices had a mean peak responsivity of 0.093 A/W at 270 nm and −15 V reverse bias

Mechanical and electrical characterization of CVD-grown graphene transferred on chalcogenide Ge2Sb2Te5layers

In the present work, we investigate some mechanical and electrical properties of a Chemical Vapor Deposition (CVD)-grown graphene layer transferred on 50 nm-thick Ge2Sb2Te5chalcogenide and discuss the possible application of graphene as a scaled contact replacing metal lines in phase-change memory devices. At first, the graphene-chalcogenide interface was extensively investigated. The expected chemical composition was confirmed by means of Electron Energy Loss Spectrometry (EELS), and the absence of bond distortions in the chalcogenide layer after graphene transfer was proved through Raman spectroscopy. The latter evidenced also the presence of defects, further confirmed by Transmission Electron Microscopy (TEM) investigations. The quality of the contact stack was evaluated by means of the adhesion among layers and by the sheet resistance of the layers themselves. Scratch tests and numerical simulations revealed a stress distribution compatible with a failure of the interface where the graphene layer features a 2 %-void. Next, the contact resistance proved an effective good Ohmic quality with a high graphene sheet resistance, about 1400 Ohm/square, which suggests that a better optimized transfer process should be applied to reduce it more than one order of magnitude