Song Bai

Design and fabrication of a 3.3 kV 4H-SiC MOSFET*

A 4H-SiC MOSFET with breakdown voltage higher than 3300 V has been successfully designed and fabricated. Numerical simulations have been performed to optimize the parameters of the drift layer and DMOSFET cell structure of active area. The n-type epilayer is 33 μm thick with a doping of 2.5 × 1015 cm−3. The devices were fabricated with a floating guard ring edge termination. The drain current Id = 5 A at Vg = 20 V, corresponding to Vd = 2.5 V.

Simulation, Fabrication and Characterization of 4500V 4H-SiC JBS Diode

4H-SiC JBS diode with breakdown voltage higher than 4.5 kV, has been successfully fabricated on 4H-SiC wafers with epitaxial layer. In this paper we report the design, the fabrication, and the electrical characteristics of 4H-SiC JBS diode. Numerical simulations have been performed to select the doping level and thickness of the drift layer and the effectiveness of the edge termination technique. The epilayer properties of the N-type are 55 μm with a doping of 9×1014 cm−3. The diodes were fabricated with a floating guard rings edge termination. The on-state voltage was 4V at JF =80 A/cm2

Radiation Resistance of Silicon Carbide Schottky Diode Detectors in D-T Fusion Neutron Detection

Silicon carbide (SiC) is a wide band-gap semiconductor material with many excellent properties, showing great potential in fusion neutron detection. The radiation resistance of 4H-SiC Schottky diode detectors was studied experimentally by carefully analyzing the detectors’ properties before and after deuterium-tritium fusion neutron irradiation with the total fluence of 1.31 × 1014 n/cm2 and 7.29 × 1014 n/cm2 at room temperature. Significant degradation has been observed after neutron irradiation: reverse current increased greatly, over three to thirty fold; Schottky junction was broken down; significant lattice damage was observed at low temperature photoluminescence measurements; the peaks of alpha particle response spectra shifted to lower channels and became wider; the charge collection efficiency (CCE) decreased by about 7.0% and 22.5% at 300 V with neutron irradiation fluence of 1.31 × 1014 n/cm2 and 7.29 × 1014 n/cm2, respectively. Although the degradation exists, the SiC detectors successfully survive intense neutron radiation and show better radiation resistance than silicon detectors.

Simulation, Fabrication and Characterization of 6500V 4H-SiC JBS Diode

4H-SiC JBS diode with breakdown voltage higher than 6.5 kV has been successfully fabricated on 4H-SiC wafers with epitaxial layer. In this paper, the simulation, the fabrication, and the electrical characteristics of 4H-SiC JBS diode were reported. The drift layer thickness and doping are 55 μm and 9×1014 cm3 respectively. 60 floating guard rings edge were fabricated as termination. The on-state voltage was 4 V at JF = 7A.

The Fabrication and Characterization of Ni/4H-SiC Schottky Diode Radiation Detectors with a Sensitive Area of up to 4 cm2

Silicon carbide (SiC) detectors of an Ni/4H-SiC Schottky diode structure and with sensitive areas of 1–4 cm2 were fabricated using high-quality lightly doped epitaxial 4H-SiC material, and were tested in the detection of alpha particles and pulsed X-rays/UV-light. A linear energy response to alpha particles ranging from 5.157 to 5.805 MeV was obtained. The detectors were proved to have a low dark current, a good energy resolution, and a high neutron/gamma discrimination for pulsed radiation, showing the advantages in charged particle detection and neutron detection in high-temperature and high-radiation environments.

Investigations on degradation and optimization of 1.2kV 4H-SiC MOSFET under repetitive unclamped inductive switching stress

In this work, the degradation mechanism of 1.2kV 4H-SiC MOSFET under repetitive Unclamped Inductive Switching (UIS) stress has been investigated. The hot-holes injection and trapping into the gate oxide above the JFET region is observed, resulting in the increase of the off-state drain-source leakage current (IDSS) and the decrease of the on-state resistance (Rdson). Moreover, an improved device with step gate oxide above the JFET region is proposed, which can effectively restrict the degradation under repetitive UIS stress, while the fresh breakdown voltage (BV) and Rdson are almost unaffected.

5A 1300V Trenched and Implanted 4H-SiC Vertical JFET

A silicon carbide (SiC) vertical channel junction field effect transistor (VJFET) was fabricated based on in-house SiC epitaxial wafer with lift-off trenched and implanted method. Its blocking voltage exceeds 1300V at gate bias VG = -6V and forward drain current is in excess of 5A at gate bias VG = 3V and drain bias VD = 3V. The SiC VJFET device’s current density is 240A/cm2 at VG= 3V and VD = 3V, with related specific on-resistance 8.9mΩ•cm2. Further analysis reveals that the on-resistance depends greatly on ohmic contact resistance and the bonding spun gold. The specific on-resistance can be further reduced by improving the doping concentration of SiC channel epilayer and the device’s ohmic contact.

213 W 500 Mhz 4H-SiC Static Induction Transistor

. Silicon carbide (SiC) SITs were fabricated using home-grown epi structures. The gate is a recessed gate - bottom contact (RG - B). We designed that the mesa space 2.7μm and the gate channel is 1.2μm. One cell has 400 source fingers and each source finger width is 100μm. 1mm SiC SIT yielded a current density of 123mA/mm of drain current at a drain voltage of 20V. A maximum current density of 150 mA/mm was achieved with Vd=40V. The device blocking voltage with a gate bias of-16 V was 200 V. Packaged 24-cm devices were evaluated using amplifier circuits designed for class AB operations. A total power output in excess of 213 W was obtained with a power density of 8.5 W/cm and gain of 8.5 dB at 500 MHz under pulse operation.

A fast-neutron detection detector based on fission material and large sensitive 4H silicon carbide Schottky diode detector

Silicon carbide radiation detectors are attractive in the measurement of the total numbers of pulsed fast neutrons emitted from nuclear fusion and fission devices because of high neutron-gamma discrimination and good radiation resistance. A fast-neutron detection system was developed based on a large-area 4H-SiC Schottky diode detector and a 235U fission target. Excellent pulse-height spectra of fission fragments induced by mono-energy deuterium-tritium (D-T) fusion neutrons and continuous energy fission neutrons were obtained. The detector is proven to be a good candidate for pulsed fast neutron detection in a complex radiation field.

Optimization of junction termination extension for ultrahigh voltage 4H-SiC planar power devices

Numerical simulations on the optimization of junction termination extension (JTE) have been performed. Various termination techniques have been applied and simulated in this paper, such as single-zone JTE (S-JTE), multi-zone JTE (M-JTE), and space-modulated JTE (SM-JTE). A completely novel and efficient method is demonstrated in this paper to determine total length of SM-JTE, and it is verified through simulation results. The simulation results show that the SM-JTE could provide a protection efficiency (defined in Section 2) of 95.2%, which is much higher than that of M-JTE (82.4%) and S-JTE (64.7%). Based on the fabricated MOSFETs, the interface charge density is extracted and the approximate range of charge density has been determined. The influences of different interface charge densities have been investigated for the three termination techniques respectively. According to the previous reports, the JTE is quite sensitive to the implanted dose, so the blocking capability of each termination structure with different implanted doses is also simulated. The results show that when interface charge is considered, the SM-JTE always shows an enormous advantage over the other two junction termination structures, however the interface charge densities varied. The space-modulated JTE is also applicable to the power planar devices such as MOSFETs and IGBTs, which would provide a very promising lower fabrication cost.