SI HETEROJUNCTION DIODES WITH A THIN BETA-SIC LAYER PREPARED WITH GAS LAYER SOURCE MOLECULAR-BEAM EPITAXY

Recently we have achieved successful growth of thin beta-SiC film on Si substrates using gas source molecular beam epitaxy (MBE) at low temperatures around 850-degrees-C. In this work, we have studied the growth of beta-SiC film on Si substrate using C2H2 gas source MBE. The films grown with C2H2 gas were analysed using various in situ (Auger electron spectroscopy, reflected high energy electron diffraction) and ex situ analysis tools (secondary ion mass spectroscopy X-ray photoelectron spectroscopy, Fourier transform IR, ellipsometry). We also have studied the C2H2 gas reaction for potential SiC atomic layer epitaxy (ALE) applications. The C2H2 gas shows a useful self-limiting reaction for the ALE process, in that C2H2 gas reacts rapidly with the highly reactive Si surface; after forming beta-SiC on the Si surface, the reaction of C2H2 gas with Si drops rapidly and further reaction of SiC is almost quenched. Finally, to study further these thin beta-SiC films, Si heterojunction diodes with a thin beta-SiC layer between heavily doped n+-type polysilicon and highly doped p-type Si layers were fabricated. The I-V curve of these diodes shows a reasonably good forward characteristic and an improved breakdown voltage compared with those of devices without the thin beta-SiC film.