Abstract
We have investigated the relationship between the electrical properties and interfacial atomic structure of SiO2/4H-SiC interfaces, prepared by dry and wet thermal oxidation procedures with 4H-SiC (0001) and 4H-SiC (000-1) substrates, using extended x-ray absorption fine structure (EXAFS) spectroscopy and electrical methods. From the current–voltage (I–V) and capacitance–voltage (C–V) measurements, the gate leakage current onset and density of interface states were shown to depend on the thermal oxidation procedure used for creating SiO2/4H-SiC (000-1) interfaces. This dependence was not observed for SiO2/4H-SiC (0001) interfaces. From EXAFS oscillations, we found that C and Si vacancies formed at the SiC side of SiO2/4H-SiC (0001) and SiO2/4H-SiC (000-1) interfaces, respectively. Compressive stress at the SiC sides of SiO2/4H-SiC (0001) and SiO2/4H-SiC (000-1) interfaces prepared with the dry thermal oxidation procedure caused decreases in bond lengths. Stress at the interface was smaller in the case of wet oxidation. Wet oxidation released the interface stress more effectively for 4H-SiC (000-1) substrates than for 4H-SiC (0001) substrates. A high gate leakage current onset related to a high interface charge, while a high density of interface states related to a high interface stress and a high interface roughness.
Highlights
IntroductionThe physical properties of silicon carbide (SiC) have enabled the commercial development of high frequency, high temperature, and high voltage power devices.[1,2,3,4,5,6,7,8,9,10] Unlike with other wide bandgap materials, an easy thermal oxidation procedure can be performed on SiC substrates to fabricate metal–oxide–semiconductor structures with SiO2 oxide layers.[7,11,12] Among the polytypes, 4H-SiC has been preferred for power device applications due to its availability as highquality wafers and its high breakdown electric field, low anisotropy, and high carrier mobility.[11,13,14,15,16] the preparation of SiO2 layers leads to high densities of interface states and the channel mobility is two orders of magnitude lower than the expected bulk mobility
We have investigated the relationship between the electrical properties and interfacial atomic structure of SiO2/4H-silicon carbide (SiC) interfaces, prepared by dry and wet thermal oxidation procedures with 4H-SiC (0001) and 4H-SiC (000-1) substrates, using extended x-ray absorption fine structure (EXAFS) spectroscopy and electrical methods
From EXAFS oscillations, we found that C and Si vacancies formed at the SiC side of SiO2/4H-SiC (0001) and SiO2/4H-SiC (000-1) interfaces, respectively
Summary
The physical properties of silicon carbide (SiC) have enabled the commercial development of high frequency, high temperature, and high voltage power devices.[1,2,3,4,5,6,7,8,9,10] Unlike with other wide bandgap materials, an easy thermal oxidation procedure can be performed on SiC substrates to fabricate metal–oxide–semiconductor structures with SiO2 oxide layers.[7,11,12] Among the polytypes, 4H-SiC has been preferred for power device applications due to its availability as highquality wafers and its high breakdown electric field, low anisotropy, and high carrier mobility.[11,13,14,15,16] the preparation of SiO2 layers leads to high densities of interface states and the channel mobility is two orders of magnitude lower than the expected bulk mobility. Thermal oxidation induces stress/strain at SiO2/SiC interface that depends on the oxidation process, thermal history, and crystal orientation.[21–25] Collectively, these results show that the interface structure and the interface chemical composition play imperative roles in the existence of interface states of
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