Papers by Keyword: Schottky

Abstract: In this work, we investigate the static electrical parameters of 1200 V 4H-SiC power diodes with various designs and architectures (Schottky, PiN, and JBS with hexagonal or stripes anode), fabricated on two types of 150 mm substrates (single crystal 4H-SiC reference and 3C-poly silicon carbide based substrates: SmartSiC^TM). I(V) measurements are carried out in both reverse and forward modes to assess the impact of designs and substrates. Non-destructive avalanche mode is reached with similar performance (leakage, V_AV) observed for both substrates (due to identical drift layers and device structures). All diode designs on SmartSiC^TM exhibit a larger current conduction and less resistance in the ohmic regime (compared to bulk), whatever the temperature (up to 200°C). Partitioning model is also proposed for evaluating the substrate contribution on the measured specific resistance and on the observed SmartSiC^TM gains.

Abstract: This paper presents a macro-and nanoscale electrical investigation of Schottky and metal-oxide junctions with hetero-epitaxial 3C-SiC layers grown on Si. Statistical current-density-voltage (J-V) characterization of Pt/3C-SiC Schottky diodes showed an increase of the reverse leakage current with increasing the devices diameters. Furthermore, C-V and J-V analyses of SiO₂/3C-SiC capacitors revealed non-idealities of the thermal oxide, such as a high trapped positive charge (3×10¹² cm⁻²) and a reduced breakdown field (E_BD=6.5 MV/cm) compared to ideal SiO₂. Nanoscale electrical characterizations by conductive atomic force microscopy (CAFM) and scanning capacitance microscopy (SCM) allowed to shed light on the origin of non-ideal behavior of Schottky and thermal oxide junctions, by correlating the morphological features associated to 3C-SiC crystalline defects with local current transport and carrier density.

Abstract: Planar Schottky contact and various trench Schottky contacts have been integrated into the edge termination region of a 4H-SiC trench metal-oxide-semiconductor field-effect-transistor (MOSFET). The forward and reverse characteristics of various design splits have been benchmarked to determine the optimum method of the Schottky contact integration. As a result, the trench Schottky diode with Schottky metal contact in both the planar surface and the trench sidewall surface has been able to offer the best performance.

Abstract: Gallium nitride (GaN) and its AlGaN/GaN heterostructures grown on large area Si substrates are promising systems to fabricate power devices inside the existing Si CMOS lines. For this purpose, however, Au-free metallizations are required to avoid cross contaminations. In this paper, the mechanisms of current transport in Au-free metallization on AlGaN/GaN heterostructures are studied, with a focus on non-recessed Ti/Al/Ti Ohmic contacts. In particular, an Ohmic behavior of Ti/Al/Ti stacks was observed after an annealing at moderate temperature (600°C). The values of the specific contact resistance ρ_c decreased from 1.6×10⁴ Ω^.cm² to 7×10⁵ Ω^.cm² with increasing the annealing time from 60 to 180s. The temperature dependence of ρ_c indicated that the current flow is ruled by a thermionic field emission (TFE) mechanism, with barrier height values of 0.58 eV and 0.52 eV, respectively. Finally, preliminary results on the forward and reverse bias characterization of Au-free tungsten carbide (WC) Schottky contacts are presented. This contact exhibited a barrier height value of 0.82 eV.

Abstract: Schottky barrier height (SBH) has been characterized on 4H-SiC Schottky diodes with metal contact of Ti/W by Current-Voltage (I-V) and Capacitance-Voltage (C-V) measurements between 80 K and 400 K. Multi-barrier has been recognized and calculated according to different models. No clear difference has been found between single barrier diode and diode with multi-barrier from DLTS tests. Evolution on the I-V characteristics has been observed after high temperature annealing. The effect of annealing at room temperature (RT) and high temperature DLTS scan (stress under high temperature) have also been studied on both static characteristics and DLTS results.

Abstract: Silicon Carbide JBS diodes are capable, in forward bias, of carrying surge current of magnitude significantly higher than their rated current, for short periods. In this work, we examine the mechanisms of device failure due to excess surge current by analyzing variation of failure current with device current and voltage ratings, as well as duration of current surge. Physical failure analysis is carried out to correlate to electrical failure signature. We also quantify the impact, on surge current capability, of the resistance of the anode ohmic contact to the p-shielding region.

Abstract: Reliability characterization of SiC devices is an ongoing activity. For this work, 650 V SiC JBS diodes in TO247 housings were tested in H3TRB. After a test period of 4000 hours none of the devices had failed during the test and only two out of sixteen devices had failed during blocking curve measurements performed at intermediate time steps. This is significantly better performance than many silicon devices offer today. The failure spots of the failed devices were detected at the edge of the main junction appearing as semi-circular cavities in the aluminum metallization. All other devices did not even show deviations from their original blocking curves.

Abstract: We report on the development of a new generation of SiC Schottky rectifier devices employing a Molybdenum based barrier metal system and a new stripe cell design for field shielding and optimized area utilization. The Schottky barrier height is reduced and thus the conduction losses are decreased significantly. The balance between forward conduction and reverse leakage losses as well as the homogeneity and stability of the new barrier system are investigated carefully.

Abstract: Wide bandgap semiconductors, such as 4H SiC, are suitable for power regulating devices, due to compatibility with conventional process integration, high breakdown voltage and thermal conductivity [1]. For RF applications, in order to achieve better switching speed, high cut off frequency, and low series resistance (Rdson), it is essential to choose the right gate metals [2]. Engineering of the gate metals not only improves the critical device parameters by adjustment of the metal workfunction, but also affects how the high aspect ratio trenches are filled for a next generation SIT device configuration [3] - [5].

Abstract: A new rectifier, called SPND or SNPD (Schottky-PN or -NP junction diode) and inherently showing low on-resistance and unipolar operation, was experimentally demonstrated for the first time on 4H-SiC. It is structured with an n^– or a p^– region of very low doping that is sandwiched and completely depleted between a Schottky junction and a one-sided PN junction. Either electrons or holes, but not both, contribute to the current conduction process. Clear and sharp rectifying properties are observed over the entire range of applied voltage.