Papers by Keyword: Power Device

Abstract: In this work, we have developed a selective wet etching technique for n+-SiC substrate using electrochemical etch process. A mixture of hydrofluoric acid and hydrogen peroxide was used as an electrolyte and the etch rates exceeding 200 μm per hour at the current density of 50 mAcm^-2 was achieved. This process is highly selective and the etching process stops at the interface of n+ SiC substrate and n-SiC epi layer. Using this process, we have successfully fabricated 180 to 250 μm thick 4’’ n-SiC epitaxial free standing wafers by separating them from a 350 μm thick n+ SiC substrate. After the substrate is completely removed, free standing wafer is characterized for wafer bow and minority carrier lifetime, using both Si-face and C-face. The wafer bow was reduced from 40 μm to 20 μm after the substrate removal. It was found that the process of removing the substrate does not introduce any extra damage to the wafer as far as the lifetime is concerned. The hole lifetime measured by microwave photoconductivity decay technique was unchanged at around 2 μsec, measured from both Si-face and C-face. These results are very promising and open up many avenues for many device applications where lightly doped free standing epitaxial semiconductor thin film is needed.

Abstract: An analytical tool to design 4H-SiC power vertical Double-diffused Metal-Oxide-Semiconductor Field-Effect-Transistor is proposed. The model optimizes, in terms of the doping concentration in the Drift–region, the trade–off between the ON–resistance, R_ON, and the maximum blocking voltage, V_BL, that is the Drain-Source voltage for which the avalanche breakdown appears at the p⁺–well/n-DRIFT junction together with the breakdown of the Gate oxide. Finding such trade-off means to maximize, Figure-Of-Merit. Our results are based on a novel full–analytical model of the electric field in the Gate oxide, E_OX, whose generality is ensured by the absence of fitting and empirical parameters. Model results are successfully compared with 2D–simulations covering a wide range of device performances.

Abstract: In this work we have studied the carbonization of 3C-SiC on misoriented Si substrates, using different thermal ramp rates and shapes. We observed that the heating rate (°C/sec) from carbonization temperature to film growth temperature plays a major role in controlling the void density. Moreover, void formation can be eliminated by the introduction of silane at different temperatures during the heating ramp. The studies were performed on a small research reactor and the results were successfully transferred to a production scale reactor, aimed to the production of 3C-SiC power devices manufactured on 100 and 150 mm Si substrates.

Abstract: The resistance of the BJT collector layer can be sharply reduced by the effective injection of minority carriers (holes) from base to collector. As a result, the voltage drop across the BJT becomes substantially lower. The conditions under which this process can occur are the short rise time and the high amplitude of the base pulse.

Abstract: Optical switch-on of a very high voltage (18-kV class) 4H-SiC thyristor with an amplification step (pilot thyristor) to the current I_max = 1225A has been demonstrated using a purely inductive load. The results obtained show that a further switch-on current increase can only be achieved by introducing additional amplification steps in the pilot thyristor structure.

Abstract: We demonstrate a novel design of large-size device in AlGaN/GaN high-electron-mobility transistor (HEMT). Depletion mode (D-mode) HEMTs and enhancement mode (E-mode) HEMTs are fabricated in our research. The saturation current of D-mode HEMTs is over 6A. By using Cascode structure, the D-mode HEMT becomes a normally-off device efficiently, and the threshold voltage of it rises from-7V to 2V. By using BCB (Benzocyclobutene) as the passivation, the E-mode HEMT shows an excellent characteristic. Also, when the V_GS of the E-mode HEMT is over 9V, it still shows a good performance.

Abstract: In this paper, I introduced the working principle and drive type of hybrid cars, and parallel hybrid system was the driver type of hybrid sanitation vehicle. Combined with vehicle parameters and power performance indicators of the original model, I matched the appropriate engine, electric motor, battery and design the corresponding transmission.

Abstract: Characteristics of high-voltage lateral silicon carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) with various reduced surface field (RESURF) structures were simulated. Breakdown voltage was enhanced from 5300 V for single-zone RESURF to 7400 V for two-zone, and to 7600 V for quasi-modulated RESURF MOSFETs.

Abstract: A 12 kV class 4H-SiC thyristor with a pilot thyristor (an amplification step) has been triggered to a current I_max = 1310 A in a mixed resistive-inductive load circuit. In order to further increase the I_max, the homogeneity of the initially turned-on region should be improved and/or additional amplification steps introduced

Abstract: Thermal performance is very important to power devices. Solder voids are detrimental to power devices thermal and reliability characteristics. According to above-mentioned problem, using computer software as an analysis tool, making some simulation and modeling on the influence of different solder voids distribution to power devices thermal characteristics. Focus on the solder voids around active region of power devices. Computing results show that solder voids under active region are the most evidently factor to power devices thermal characteristics and provide some suggests on the process of power devices thermal design.