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A novel taper-doping anode termination method is introduced for high-voltage silicon carbide devices. The method employs a subresolution two-tone termination mask to achieve a gray-scale exposure and a smoothly tapered photoresist profile. Using the tapered profile as an implantation mask, self-aligned 6-kV SiC PiN diodes are demonstrated with 90% of the parallel-plate breakdown voltage. The avalanche breakdown for the design is controlled and reversible. This one-step technique allows wide design control over the width and shape of the termination profile and has wide device and material applicability. [ABSTRACT FROM AUTHOR]

We present X-ray photoelectron spectroscopy, van der Pauw Hall mobilities, low-temperature far-infrared magneto transmission (FIR-MT), and atomic force microscopy (AFM) results from graphene films produced by radiative heating in an ultrahigh vacuum (UHV) chamber or produced by radio frequency (RF) furnace annealing in a high vacuum chemical vapor deposition system on Si- and C-face 4H SiC substrates at 1200−1600 °C. Although the vacuum level and heating methods are different, graphene films produced by the two methods are chemically similar with the RF furnace annealing typically producing thicker graphene films than UHV. We observe, however, that the formation of graphene on the two faces is different with the thicker graphene films on the C-face RF samples having higher mobility. The FIR-MT showed a 0(−1) → 1(0) Landau level transition with a √B dependence and a line width consistent with a Dirac fermion with a mobility >250 000 cm2·V−1·s−1at 4.2 K in a C-face RF sample having a Hall-effect carrier mobility of 425 cm2·V−1·s−1at 300 K. AFM shows that graphene grows continuously over the varying morphology of both Si and C-face substrates. [ABSTRACT FROM AUTHOR]

This paper reports on a 4H-SiC single-photon avalanche diode (SPAD) operating at UV wavelengths of 280 and 350 nm. The SPAD shows low dark currents of 20 and 57 fA at 80 V and 90% breakdown voltage, respectively. The quantum efficiency (QE) reaches its peak of 43% at 270 nm and is < 0.007% at 400 nm, indicating a high UV-to-visible rejection ratio of > 6100. The 4H-SiC SPAD shows a fast self-quenching and a high photon count rate of 1.44 MHz in the passive-quenching mode. At the wavelength of 280 nm, a single-photon detection efficiency (SPDE) of 2.83% with a low dark count rate of 22 kHz is achieved at the reverse bias of 116.8 V. The SPDE at 350 nm is lower, which is 0.195%, owing to the correspondingly smaller QE. Optimization measurements were conducted on SPDE as a function of voltage bias and signal output threshold. [ABSTRACT FROM AUTHOR]

Heterojunctions of p+ B-doped nanocrystalline diamond (NCD) to n- 4H-SiC were studied by electrical and cathodoluminescence (CL) methods. Current rectification at 30 °C had a curvature coefficient γ0 of 42.1 V-1 at zero bias, γmax of 105.35 V-1 at 0.2 V, and a reverse current of <10 nA/cm2. The NCD sheet resistance decreased from 4.1×1011 to 403.56 Ω/sq. as the carrier density Ns was increased from 3.5×105 to 1.5×1016 cm-2 by B2H6 doping. The 348 cm2/V-s mobility of the B-free NCD films was comparable to that of single crystal diamond. CL data revealed traps 0.6-0.8 eV from the NCD EV edge. [ABSTRACT FROM AUTHOR]