Victor V. Luchinin

Superfast Drift Step Recovery Diodes (DSRDs) and Vacuum Field Emission Diodes Based on 4H-SiC

This paper presents the results of research and development of two types diode structures based on wide bandgap 4H-SiC: drift step recovery diodes (DSRDs) and field emission diodes (FED). Diodes’ structure and manufacturing methods are reviewed. Diode’s characteristics were obtained (static current-voltage characteristics and capacitor-voltage characteristic, switching properties’ characteristics for DSRDs). Field emission 4H-SiC structures illustrated high (≥102 А/сm2) current densities at electric field intensity of approximately 10V/um. 4H-SiC DSRDs in the generator structure with a single oscillating contour allowed to form sub nanosecond impulses at a load 50 Ohm and 1,5-2kV amplitude for a single diode (current density at V=2kV J= 4•103 А/сm2),what is significantly higher than similar DSRD’s parameters obtained for silicon.

High-Voltage Ultra-Fast Pulse Diode Stack Based on 4H-SiC

The paper reports on the results of the studies of static and dynamic characteristics of 4H-SiC drift step recovery diodes (DSRDs) assembled in diode stacks. Switching performance of single dies has been simulated and experimentally confirmed. It was established that the switching process is determined primarily by the incomplete ionization of acceptors in 4H-SiC and by the bandgap narrowing in heavily doped emitters. Based on the simulation results the optimized die size has been selected. For DSRD stacks of 4 and 8 dies I-V and C-V measurements are reported. The stacks were dynamically tested in a special oscillator circuit. Repetitive voltage pulses of 10.5 kV with the leading edge length of 900 ps were demonstrated.

Effect of Phosphorus Implantation Prior to Oxidation on Electrical Properties of Thermally Grown SiO2/4H-SiC MOS Structures

The electrical properties of metal-oxide-semiconductor (MOS) devices fabricated using dry oxidation on phosphorus-implanted n-type 4H-SiC (0001) epilayers have been investigated. MOS structures were compared in terms of interface traps and reliability with reference sample which was produced by dry oxidation under the same conditions. The notably lower interface traps density measured in MOS capacitor with phosphorus concentration exceeding 1018 cm-3 at the SiO2/SiC interface was attributed to interface traps passivation by incorporated phosphorus ions.

Passivation of 4H-SiC/SiO2 Interface Traps by Oxidation of a Thin Silicon Nitride Layer

The effect of the alternative nitridation process of the 4H-SiC/SiO2 interface by introduction of a thin silicon nitride layer on the electrical properties of the gate oxide has been investigated. C-V and G-V measurements on inversion-channel MOS devices revealed similar results to the conventional N2O oxidation. Higher field-effect mobility values are achieved due to lower interface roughness of the alternative nitridation process. However, insignificant degradation of the reliability was observed.

Inversion-Channel MOS Devices for Characterization of 4H-SiC/SiO2 Interfaces

Electrical properties of the gate oxides thermally grown in N2O on n-type and p-type 4H-SiC have been compared using conventional MOS structure and inversion-channel MOS structure, respectively. Sufficient difference in the electrical properties of the gate oxides grown on n-type and p-type 4H-SiC was revealed. We conclude that the gate oxide process optimisation using inversion-channel MOS devices is superior as compared to the conventional MOS structure.

High Channel Mobility 4H-SiC MOSFETs by As and P Implantation Prior to Thermal Oxidation in N2O Atmosphere

High channel mobility 4H-SiC MOSFETs have been demonstrated by phosphorus and arsenic implantation prior to thermal oxidation in N2O. The maximum field-effect mobility of 81 and 114 cm2/Vs were achieved, respectively. The MOSFET fabrication was done on lightly aluminium doped p-type epitaxial layers and on heavily aluminium implanted p-well.

Temperature Dependence of Minority Carrier Lifetime in Epitaxially Grown p+-p–-n+ 4H-SiC Drift Step Recovery Diodes

In this paper we report on the effect of temperature and injection level on the effective lifetime of non-equilibrium charge carriers in p-base of 4H-SiC PiN diodes. Studies were carried out on 1kV drift step recovery diodes (DSRDs) with p+-p--n+. The lifetime of non-equilibrium charge carriers in 4H-SiC p+-p--n+ structures increases by an average of 6 times from 250ns to 1.4μs with the increase of the samples temperature from 300K to 673K. However, increase of the injection level in the drift region from 2.3·1016cm-3 to 5.9·1016cm-3 does not affect the lifetime indicating that Shockley-Read-Hall recombination processes are dominating.

Effect of neutron irradiation on epitaxial 4H-SiC PiN UV-photodiodes

4H-SiC UV-photodetectors based on full-epitaxial p +p-n+ multilayer structures werefabricated. The diodes were irradiated with fast neutrons up to the fluence of 1·1014 cm-2 . Current-voltage characteristics, life time of non-equilibrium charge carriers as well as photosensitivityspectra of the diodes before and after irradiation were investigated. The studies showed that PiNUV-photodiodes with base doping below 1·1015 cm-3 retain their performance up to the fluence of5·1012 neutrons per cm2 . The further increase in fast neutron fluence stimulates the creation ofexcessive deep recombination centers. This leads to degradation of I-V-characteristics, reduction ofcarrier life time and, consequently, to degradation of the photosensitivity of devices.

Tailoring the 4H-SiC/SiO2 MOS-interface for SiC-based power switches

In this paper, we compare the performance of lateral MOSFETs fabricated with different gate oxide formation processes on p-type epilayers with doping concentration in the range of 1 × 1016 cm−3 against Al-implanted p-well doped to 1 × 1018 cm−3. An overview of different technological approaches for the enhancement of the channel mobility is provided. The general trends are summarized and concluded and the main guideline for tailoring the gate oxide formation process is discussed.

Micromechanics Based on Silicon Carbide

This paper describes using of silicon carbide for micromechanical systems. Low stressed sensitive membrane signal converters, thin film transducers and piezoresistive sensors were formed based on silicon carbide films. The mechanical properties of silicon carbide films were determined.