Inversion channel MOSFET on heteroepitaxially grown free-standing diamond

Abstract

We successfully fabricated the inversion-type p-channel metal–oxide–semiconductor field-effect transistor (MOSFET) on heteroepitaxially grown free-standing diamond using silicon-based substrates. The drain current–drain voltage (Ids–Vds) and drain current–gate voltage (Ids–Vgs) characteristics were examined. The maximum drain current density and the peak field effect mobility (μFE) were around 0.35 mA/mm and 2.7 cm2 V−1s−1, which were lower than our reported results of the homoepitaxial diamond MOSFETs fabricated on high-pressure, high-temperature (HPHT) substrates. The interface state density (Dit) extracted from the subthreshold region was around 5.5 × 1012 cm−2eV−1, comparable to our reported results of the homoepitaxial diamond MOSFET. To further examine the reason for the low μFE, atomic force microscopy (AFM) measurements were performed for the n-type body of the heteroepitaxial diamond MOSFET, and we found that the surface roughness was much larger than our reported ones of the homoepitaxial diamond MOSFET. It can be deduced that the surface roughness would be one main limiting factor for the field effect mobility of the heteroepitaxial diamond MOSFET. The imperfect diamond heteroepitaxy would also degrade the field effect mobility. This work explores the potential of the inversion-type p-channel heteroepitaxial diamond MOSFETs, which would facilitate the practical application of diamond power devices.