Varactor diodes of hydrogenated nanocrystalline Si with hydrogenated amorphous SiC prepared by PECVD

Abstract

Hetero-structural barrier varactor diodes (HBVDs) can be widely used as variable capacitors, frequency multipliers, parametric amplifiers, etc. in electronic systems. Herein, n-type hydrogenated nano-crystalline Si (n-nc-Si:H) films with narrow band-gap and un-intentional doped hydrogenated amorphous SiC (a-SiC:H) ones with wide band-gap are adopted to innovatively design the n-nc-Si:H/a-SiC:H/n-nc-Si:H-based HBVDs. Two periodic hetero-structures with different doped nc-Si:H modulation layers and different thickness a-SiC:H barriers are severally fabricated by plasma enhanced chemical vapor deposition (PECVD), the optical band-gaps of n-nc-Si:H and a-SiC:H are derived from the ultra violet-visible (UV–vis) absorption spectra, the prepared devices are demonstrated as the HBVDs by measuring the relations of current density–voltage and capacitance–voltage, respectively. The conduction mechanisms of the fabricated devices in different biased voltage ranges are probed, the variation of capacitance modulation ratio with changing the doped-level in modulation layers and thickness of barriers are analyzed. This paper will be helpful to extend the material combination and preparation method for HBVDs.