SiC 4H: August 2018

Aug 16, 2018

Experimental investigation of slow-positron emission from 4H-SiC and 6H-SiC surfaces

Slow-positron emission from the surfaces of as-grown n-type 4H-SiC and 6H-SiC (silicon carbide) with a conversion efficiency of ~ 10−4 has been observed. After 30 min of 1000 oC annealing in forming gas, the conversion efficiency of the n-type 6H-SiC sample was observed to be enhanced by 75% to 1.9 × 10−4, but it then dropped to ~ 10−5 upon a further 30 min annealing at 1400 oC. The positron work function of the n-type 6H-SiC was found to increase by 29% upon 1000 oC annealing. For both p-type 4H-SiC and p-type 6H-SiC materials, the conversion efficiency was of the order of ~ 10−5, some ten times lower than that for the n-type materials. This was attributed to the band bending at the p-type material surface which caused positrons to drift away from the positron emitting surface.

Source:IOPscience

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Aug 3, 2018

Schottky barrier height modification of metal/4H-SiC contact using ultrathin TiO2 insertion method

The fabrication processes, electrical characteristics, and reliability of the Schottky barrier diodes (SBDs) on an n-type 4H-silicon carbide (SiC) substrate are investigated. To modulate the Schottky barrier height (SBH), titanium dioxide (TiO2) is inserted at the interface between the metal and the SiC substrate. Ni, Mo, Ti, and Al are chosen to form SBDs. The maximum SBH modulation of 0.3 eV is obtained with a 5-nm-thick TiO2 layer. The SBH pinning factors of the SBDs without TiO2insertion and with 2-nm-thick TiO2 insertion are similar. Therefore, the mechanism of the SBH modulation is attributed to the interface dipole-induced potential drop. Finally, the reliability of the SBD with TiO2 insertion is evaluated. The SBH, ideality factor, and reverse leakage current are stable after high forward current stress at 300 A/cm2 for 15000 s. This work provides a simple method to modulate the SBH on SiC and is feasible for SBD application.