Selective Fabrication of SiC/Si Heterojunction Diodes by Local Laser Annealing Process for Microwave Circuit Applications

This paper presents the RF characterization of SiC/Si heterojunction diodes fabricated using a novel localized laser process. Selective growth of SiC on Si is carried out by utilizing excimer laser-based annealing in the presence of carbon source. Use of ambient conditions (atmospheric pressure and room temperature) during growth makes this process simple and low cost. The Si wafer is first coated with carbon rich film and then locally annealed using high power laser which causes dissociation of solid carbon sources and a simultaneous melting of the silicon leading to the growth of SiC. The Raman spectrum shows peaks for acoustical and optical phonon modes for β-SiC between 940 and 980 cm^-1. The fabricated diodes show high breakdown voltage (>200 V) and low leakage current density of 3-5 μA/cm² (-5 V). Experimental results for the dc characteristics, microwave rectification and frequency multiplication are presented. The measured results show good RF rectification (e.g., 21 V/W at 3 GHz) up to 6 GHz using a large diode (70×70 μm²). The diodes also work well as frequency doublers over a wide frequency range of 2-6 GHz. The diode area can be scaled down to design circuits operating at higher frequencies.