The improvement of Mo/4H-SiC Schottky diodes via a P2O5 surface passivation treatment

Molybdenum (Mo)/4H-silicon carbide (SiC) Schottky barrier diodes have been fabricated with a phosphorus pentoxide (P2O5) surface passivation treatment performed on the SiC surface prior to metallization. Compared to the untreated diodes, the P2O5-treated diodes were found to have a lower Schottky barrier height by 0.11 eV and a lower leakage current by two to three orders of magnitude. Physical characterization of the P2O5-treated Mo/SiC interfaces revealed that there are two primary causes for the improvement in electrical performance. First, transmission electron microscopy imaging showed that nanopits filled with silicon dioxide had formed at the surface after the P2O5 treatment that terminates potential leakage paths. Second, secondary ion mass spectroscopy revealed a high concentration of phosphorus atoms near the interface. While only a fraction of these are active, a small increase in doping at the interface is responsible for the reduction in barrier height. Comparisons were made between the P2O5 pretreatment and oxygen (O2) and nitrous oxide (N2O) pretreatments that do not form the same nanopits and do not reduce leakage current. X-ray photoelectron spectroscopy shows that SiC beneath the deposited P2O5 oxide retains a Si-rich interface unlike the N2O and O2 treatments that consume SiC and trap carbon at the interface. Finally, after annealing, the Mo/SiC interface forms almost no silicide, leaving the enhancement to the subsurface in place, explaining why the P2O5 treatment has had no effect on nickel- or titanium-SiC contacts

Diamond semiconductor technology for RF device applications

This paper presents a comprehensive review of diamond electronics from the RF perspective. Our aim was to find and present the potential, limitations and current status of diamond semiconductor devices as well as to investigate its suitability for RF device applications. While doing this, we briefly analysed the physics and chemistry of CVD diamond process for a better understanding of the reasons for the technological challenges of diamond material. This leads to Figure of Merit definitions which forms the basis for a technology choice in an RF device/system (such as transceiver or receiver) structure. Based on our literature survey, we concluded that, despite the technological challenges and few mentioned examples, diamond can seriously be considered as a base material for RF electronics, especially RF power circuits, where the important parameters are high speed, high power density, efficient thermal management and low signal loss in high power/frequencies. Simulation and experimental results are highly regarded for the surface acoustic wave (SAW) and field emission (FE) devices which already occupies space in the RF market and are likely to replace their conventional counterparts. Field effect transistors (FETs) are the most promising active devices and extremely high power densities are extracted (up to 30 W/mm). By the surface channel FET approach 81 GHz operation is developed. Bipolar devices are also promising if the deep doping problem can be solved for operation at room temperature. Pressure, thermal, chemical and acceleration sensors have already been demonstrated using micromachining/MEMS approach, but need more experimental results to better exploit thermal, physical/chemical and electronic properties of diamond

Surface acoustic wave/silicon monolithic sensor/processor

A new technique for sputter deposition of piezoelectric zinc oxide (ZnO) is described. An argon-ion milling system was converted to sputter zinc oxide films in an oxygen atmosphere using a pure zinc oxide target. Piezoelectric films were grown on silicon dioxide and silicon dioxide overlayed with gold. The sputtered films were evaluated using surface acoustic wave measurements, X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, and resistivity measurements. The effect of the sputtering conditions on the film quality and the result of post-deposition annealing are discussed. The application of these films to the generation of surface acoustic waves is also discussed

Silicon crystal as a low work function collector

A test vehicle with a low work function collector which can be incorporated in a thermionic converter was constructed from standard vacuum components including an ultrahigh vacuum ion pump. The collector assembly was fabricated by diffusion bonding a (100) oriented silicon single crystal to a molybdenum block. The silicon surface was treated with cesium and oxygen to produce an NEA-type condition and the results were tested by photoemission and work function measurements. An n-type silicon collector was successfully activated to a work function of 1.0 eV, which was verified by photoemission spectral yield measurements. The stability test of an activated surface at elevated temperatures was conducted in the range from room temperature to 619 K, which was slightly lower than the designed collector temperature of 700 K. The work function measurements clearly demonstrated that the behavior of cesium replenishment on the activated Si surface was similar in nature to that of a metallic surface; that is, the loss of cesium by thermal desorption could be compensated by maintaining an adequate vapor pressure of cesium

Fabrication and Characterization of CIS/CdS and Cu2S/CdS Devices for Applications in Nano Structured Solar Cells

Nano structured solar cells provide an opportunity for increased open circuit voltages and and short circuit currents in solar cells due to quantum confinement of the window and absorber materials and an increase in the optical path length for the incident light. In this study, both bulk and nano heterojunctions of CIS/CdS and Cu2S/CdS devices have been fabricated and studied on plain glass substrates and inside porous alumina templates to compare their performance. The devices have also been characterized SEM, XRD and JV measurements. The J-V curves have also been analyzed for series resistance, diode ideality factor and reverse saturation current density