Papers by Author: Jesse B. Tucker

Abstract: 4H-SiC MOS capacitors were used to characterize the effect of reactive-ion etching of the SiC surface on the electrical properties of N2O-grown thermal oxides. The oxide breakdown field reduces from 9.5 MV/cm with wet etching to saturate at 9.0 MV/cm with 30% reactive-ion over-etching. Additionally, the conduction-band offset barrier height, φB, progressively decreases from 2.51 eV with wet etching to 2.46 eV with 45% reactive-ion over-etching.

Abstract: Results of a 1200V 4H-SiC vertical DMOSFET based on ion implanted n+ source and pwell regions are reported. The implanted regions are activated by way of a high temperature anneal (1675°C for 30 min) during which the SiC surface is protected by a layer of graphite. Atomic force microscopy shows the graphite to effectively prevent surface roughening that otherwise occurs when no capping layer is used. MOSFETs are demonstrated using the graphite capped anneal process with a gate oxide grown in N2O and show specific on-resistance of 64 mW×cm2, blocking voltage of up to 1600V and leakage current of 0.5–3 ´10-6 A/cm2 at 1200V. The effective nchannel mobility was found to be 1.5 cm2/V×s at room temperature and increases as temperature increases (2.8 cm2/V×s at 200°C).

Abstract: Depletion-mode 4H-SiC FETs were fabricated for use as harsh environment gas sensors. To enable sensitivity to NOx, O2 and H2 gases, metal oxide catalysts such as InOx were integrated into the gate of the device. The FETs had a total area of approximately 1 mm2. Devices with various gate widths and lengths were fabricated and tested, with sensor performance of 5% or greater in current change from the baseline resulting from designs having a length to width ratio of around 50.

Abstract: Different SiC thermal oxide passivation techniques were characterized using UV-induced hysteresis to estimate the fixed charge, Qf, and interface-trapped charge, Qit. Steam-grown oxides have a fixed charge density of Qf=-1x1012 cm-2, and a net interface-trapped charge density of Qit=4x1011cm-2. Addition of a thin low-pressure chemical-vapor deposited (LPCVD) silicon nitride layer decreased these parameters to Qf=-2x1011 cm-2 and Qit=4x1010 cm-2. Dry oxide shows a fixed charge density, Qf=-3x1012 cm-2 and interface-trapped charge density, Qit=4x1011 cm-2 which changes to Qf=+7x1010 cm-2 and Qit=1x1010 cm-2 with the addition of a LPCVD silicon nitride cap. Dry thermal oxide with a silicon nitride cap was used to passivate SiC MESFETs to achieve a power-added efficiency of 60% in pulsed operation at 3 GHz in Class AB bias conditions.