Modest channel carrier mobility in SiC-MOSFETs with NO annealed gate oxides has been the main factor hampering development of low power devices (300 – 650 V). A very fast interface trap, noted as NI, has been suggested to be the main culprit for poor inversion channel carrier mobility. The origin of the NI trap is unknown, but it is likely a property of the SiO2 and it is enhanced during post nitridation. In this study we show that the NI trap is also detected in 4H-SiC/AlN and 4H-SiC/Al2O3 MIS-capacitors. Observations are done using conductance spectroscopy and capacitance voltage measurements at cryogenic temperatures. This strongly suggests that the NI trap is a property of the SiC surface and not the dielectric used to form the SiC/dielectric interface. Furthermore, a scanning transmission electron microscopy (STEM) was performed to confirm that there are no SiO2 layers or islands present at the 4H-SiC/AlN and 4H-SiC/Al2O3 interfaces.

Very fast interface traps have recently been suggested to be the main cause behind poor channel-carrier mobility in SiC metal-oxide-semiconductor field effect transistors. It has been hypothesized that the NI traps are defects located inside the SiO2 dielectric with energy levels close to the SiC conduction band edge and the observed conductance spectroscopy signal is a result of electron tunneling to and from these defects. Using aluminum nitride and aluminum oxide as gate dielectrics instead of SiO2, we detect NI traps at these SiC/dielectric interfaces as well. A detailed investigation of the NI trap density and behavior as a function of temperature is presented and discussed. Advanced scanning transmission electron microscopy in combination with electron energy loss spectroscopy reveals no SiO2 at the interfaces. This strongly suggests that the NI traps are related to the surface region of the SiC rather than being a property of the gate dielectric.

The hot-wall metalorganic chemical vapor deposition (MOCVD) concept, previously shown to enable superior material quality and high performance devices based on wide bandgap semiconductors, such as Ga(Al)N and SiC, has been applied to the epitaxial growth of beta-Ga2O3. Epitaxial beta-Ga2O3 layers at high growth rates (above 1 mu m/h), at low reagent flows, and at reduced growth temperatures (740 degrees C) are demonstrated. A high crystalline quality epitaxial material on a c-plane sapphire substrate is attained as corroborated by a combination of x-ray diffraction, high-resolution scanning transmission electron microscopy, and spectroscopic ellipsometry measurements. The hot-wall MOCVD process is transferred to homoepitaxy, and single-crystalline homoepitaxial beta-Ga2O3 layers are demonstrated with a 201 rocking curve width of 118 arc sec, which is comparable to those of the edge-defined film-fed grown (201) beta-Ga2O3 substrates, indicative of similar dislocation densities for epilayers and substrates. Hence, hot-wall MOCVD is proposed as a prospective growth method to be further explored for the fabrication of beta-Ga2O3.