Observation of a two dimensional electron gas formed in a polarization doped C-face 3C∕4H SiC heteropolytype junction

A two dimensional electron gas (2DEG) was observed in a C-face 3C∕4H SiC heteropolytype junction. Sheet carrier concentrations of ∼3×1013cm−2 and Hall mobility of ∼314cm2∕Vs were measured at 77K. The temperature dependences of mobility and carrier concentration clearly demonstrate the presence of the 2DEG. Comparison with theory indicates that the carriers originate from both spontaneous polarization and unintentional degenerate nitrogen doping of 3C-SiC, suggesting a 77K 2DEG mobility ∼700cm2∕Vs in parallel with bulk hopping conduction. Mobility at high temperatures was phonon limited, indicating a Debye temperature of 1600K. Transmission line measurements yielded similar mobilities, with saturation currents of ∼3A∕mm, suggesting the utility of SiC heteropolytypes in microwave devices.