Aluminum doped silicon carbide thin films prepared by hot-wire CVD: Investigation of defects with electron spin resonance

Al-doped p-type μc-SiC:H is prepared in a wide range of HWCVD preparation parameters like Al-doping ratio, deposition pressure, substrate and filament temperatures. We investigate the structural and electrical properties, and focus on identification of paramagnetic defect states by electron spin resonance (ESR). Nominally undoped μc-SiC:H is of a high n-type conductivity (σD = 10− 6–10− 1 S/cm) and shows a narrow central ESR line (g ≈ 2.003, peak-to-peak linewidth ∆Hpp ≈ 4 G) with two pairs of satellites and a spin density NS = 1019 cm− 3. Al-doping results in the compensation of dark conductivity to as low as σD = 10− 11 S/cm and at higher doping concentrations to effective p-type material. Increase of Al-doping results in reduction of crystallinity (ICIR), ESR line shifts to g ≈ 2.01 and becomes as broad as ∆Hpp ≈ 30 G, not unlike to the resonance of singly occupied paramagnetic valence band tail states in a-Si:H. ESR spectrum of highly crystalline Al-doped μc-SiC:H however has a g-value very close to undoped μc-SiC:H. Electron spin density in compensated material decreases to 5 × 1017 cm− 3 before it increases again for the highly doped material.