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Five Σ-shaped dislocation arrays in 100-mm-diameter, 12-μm-thick 4H-SiC epitaxial wafers were observed using photoluminescence mapping. The structure of the Σ-shaped dislocation arrays was characterized using nondestructive analytical techniques of photoluminescence mapping, microphotoluminescence spectroscopy, and x-ray topography. Each Σ-shaped dislocation array consists of two basal plane dislocations (BPDs) at the interfacial dislocation terminal points and two half-loop arrays. The interfacial dislocation pairs nucleate from BPDs in the substrate. Three independent stresses lead to interfacial dislocations: thermal stress (τT), stress induced by misfit strain (τM), and interaction force (τI). The main cause of interfacial dislocation formation is attributed to the development of τT within the wafer due to temperature nonuniformity. τM and τI also contribute to the formation of interfacial dislocations. Larger stresses increase the BPD glide velocity in the interfacial dislocations, thereby producing longer Σ-shaped dislocation arrays.

Trap levels play an important role in semiconductor power devices. The barrier height of a metal-semiconductor junction, one of the important factors of unipolar devices, is influenced by the trap levels at its interface, i.e., interface states. However, there has not been much research on the interface states of Schottky diodes yet. Here, we report newly found KI1, KI2, and KI3 interface states of 4H-SiC Schottky diodes. We observed their changes after the first deep-level transient spectroscopy measurements, in which temperature rises to 750 K, and discussed the origins of these changes by using X-ray photoelectron spectroscopy and scanning electron microscopy. The KI1 was related to oxygen and photoresist (PR) residue, the KI2 was related to oxygen, and the KI3 was related to the PR residue.

We have developed an instrument for real-time observation of silicon carbide (SiC) crystal during the sublimation growth process by x-ray topography. It is constructed by combining an x-ray goniometer and a crystal-growth chamber. The vertical goniometer consists of three circles, an α circle for the x-ray source, a β circle for the detector, and a φ circle for the azimuthal rotation of the sample. The growing crystal boule is set at the center of the goniometer glued on a crucible lid. Transmission topographs are taken using an asymmetric (1011) reflection with the scattering angle 2θB=β−α from the (0001)-oriented boule. A rotating-anode 18 kW generator with a molybdenum target is employed as the x-ray source. Topographs are observed by a direct imaging system using a charge-coupled device camera. Incident and scattered x-ray beams pass through beryllium windows mounted on the bottom and top flanges of the crystal-growth chamber, respectively. The crucibles are also designed for in situ measurements so ...

The Au/Ni/Al2O3/4H-SiC junction with the Al2O3 film as a thin spacer layer was found to show the electrical characteristics of a typical rectifying Schottky contact, which is considered to be due to the leakiness of the spacer layer. The Schottky barrier of the junction was measured to be higher than an Au/Ni/4H-SiC junction with no spacer layer. It is believed that the negative surface bound charge originating from the spontaneous polarization of 4H-SiC causes the Schottky barrier increase. The use of a thin spacer layer can be an efficient experimental method to modulate Schottky barriers of metal/4H-SiC junctions.

A non‐toxic and non‐flammable organosilicon source having alternate Si–C bonding structure, bis‐trimethylsilylmethane [C7H20Si2], was first used to deposit epitaxial β‐SiC films at low growth temperature by chemical vapor deposition. Epitaxial β‐SiC films were successfully grown on carburized Si(100) substrates at temperatures as low as 1100 °C, although the carburized buffer layer was a well‐oriented, (100) polycrystalline film. Transmission electron microscopy analysis revealed that the films contain twins, stacking faults, and antiphase boundaries. Without the carburized buffer layer, highly (111) preferred oriented β‐SiC films were grown by increasing the growth temperature.

In this letter, we have reported electrical and physical properties of rapid thermal annealed (RTA) Al2O3 stacking dielectric on n-type 4H-SiC. The effects of SiN-reaction barrier layer (RBL) between Al2O3 and thermal-nitrided SiO2 on SiC-based metal-oxide-semiconductor characteristics have been investigated and compared. A significant reduction in oxide-semiconductor interface-trap density (Dit), improvement in dielectric breakdown field and reliability has been observed after the SiN-RBL has been introduced between Al2O3 and SiO2. High-resolution transmission electron microscope and Auger electron spectroscopy analyses reveal that the SiN-RBL suppresses Al diffusion into the nitrided SiO2 during RTA process.

The atomic force microscopy-based local oxidation (AFM-LO) of silicon carbide (SiC) is extremely difficult in general, mainly due to their physical hardness and chemical inactivity. Herein, we report the strongly enhanced AFM-LO of 4H-SiC at room temperature without the heating, chemicals or photoillumination. It is demonstrated that the increased tip loading force (∼>100 nN) on the highly doped SiC can produce a high enough electric field (∼8×106 V/cm) under the cathode tip for transporting oxyanions, thereby leading to direct oxide growth on 4H-SiC. The doping concentration and electric field profile of the tip-SiC sample structures were further examined by two-dimensional numerical simulations.

In this paper, current conduction mechanisms of an atomic-layer-deposited HfO2 gate stacked on different thicknesses of thermally nitrided SiO2 based on n-type 4H SiC have been investigated and analyzed. Current-voltage and high-frequency capacitance-voltage measurements conducted at various temperatures (25−140 °C) were performed in metal-oxide-semiconductor test structures with 13 nm thick HfO2 stacked on 0-, 2-, 4-, or 6 nm thick nitrided SiO2. Various conduction mechanisms, such as Schottky emission, Fowler-Nordheim tunneling, Poole-Frenkel emission, and space-charge-limited conduction, have been systematically evaluated. The mechanisms of the current conducted through the oxides were affected by the thickness of the nitrided oxide and the electric field applied. Finally, current conduction mechanisms that contributed to hard and soft dielectric breakdown have been proposed.

Current conduction mechanisms of an atomic-layer-deposited Al2O3 gate on n-type 4H SiC have been systematically investigated, analyzed, and reported in this letter. It has been revealed that space charge limited, Poole-Frenkel (PF) emission, combination of PF emission and Fowler-Nordheim tunneling are the dominate current conduction mechanisms in the dielectric. Besides, Schottky emission has also been proposed as a possible leakage path at temperature beyond the investigated range. A relationship among the conduction mechanism, temperature, and applied electric field has been presented.

The effects of thermal nitrided gate-oxide thickness on n-type 4H silicon-carbide-based metal-oxide-semiconductor characteristics have been reported. Seven different thicknesses of oxide (tox), ranging from 2to20nm, have been investigated. It has been shown that effective oxide charge (Qeff) and total interface-trap density (Nit) have demonstrated a cyclic trend as tox is increased. These observations have been explained in the letter. Correlations of Qeff and Nit with oxide breakdown field and current transport mechanism in these oxides have also been established and explained.

In this letter we report current-conduction mechanisms in nitrided gate oxides on n-type 4H SiC subjected to various rapid-thermal-annealing temperatures. The experimental results show that by increasing SiC-SiO2 interface trap density, current conduction in the oxide is increased. Fowler-Nordheim (FN) tunneling which is assisted by SiC-SiO2 interface trap is responsible to the current conduction. In contrast, the current conduction through the oxide is significantly reduced when the oxide is having a multiple discrete energy level of electron trap center. This center enables trapping of electrons that are injected from SiC substrate via FN tunneling, causing a reduction in leakage current and an improvement in oxide breakdown strength. Based on the results, a model has been hypothesized and reasons for these observations have been presented.