Semi-insulating porous SiC substrates

Semi-insulating SiC substrates were fabricated on a base of porous silicon carbide made from 4H and 6H commercial SiC wafers. Porous SiC (PSC) layers, 3 µm in thickness, were made by surface anodization of SiC wafers and then impregnated with excessive Si from a sputtered SiO₂ film during thermal processing at 1200 °C. The processed structures were studied by Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and x-ray photoelectron spectroscopy (XPS). The Si/C ratio in the processed porous layers showed a measurable change from 1:1 to 2.3:1 due to the diffusion of Si from the SiO₂ film into the PSC layer during thermal processing. The value of specific resistivity achieved was found to be 5 × 10¹¹ Ω cm at 470 K and 2 × 10⁶ Ω cm at 700 K, respectively, with an activation energy of resistivity of 1.53 eV. Preliminary evaluations of AlN films grown by HVPE on the prepared substrates are also presented.