Papers by Author: Andrey O. Konstantinov

Abstract: High power high efficiency silicon carbide RF MESFETs are fabricated using a novel structure utilizing lateral epitaxy. The MESFET employs buried p-type depletion stoppers grown by lateral epitaxy with subsequent planarization. The depletion stopper is epitaxially overgrown by the channel layer. The depletion stopper suppresses short channel effects and increases the operation voltage and the RF signal gain at high voltage operation. High breakdown voltages of over 200 Volts are achieved for single-cell components, however large-area transistors are limited to around 150 Volts. Single-cell components measured on-wafer demonstrate an Ft of 10 GHz and high unilateral gain. Packaged 6-mm RF transistors in amplifier circuits feature a saturated power of 20 W and a P1dB of 15W with a linear gain of over 16 dB at Vdd of 60 V for 2.25 GHz operation. Maximum drain efficiency is 56% for class AB operation, 48% at 1 dB compression point and 72% for class C at 2.25 GHz.

Abstract: The spectrometric characteristics of the detectors based on 4H-SiC using 4.8-7.7 MeV a-particles were determined. The Cr Schottky barriers with areas of 1×10-2 cm2 were performed^by vacuum thermal evaporation on 4H-SiC epitaxial layers grown by chemical vapor deposition (CVD) with thickness 26 and 50 µm. The concentrations of the uncompensated donors into CVD epitaxial layers were (6-10) ×1014 cm-3, that allowed to develop a detector depletion region up to 30 µm using reverse bias of 400 V. The energy resolution less than 20 keV (0.34%) for lines of 5.0- 5.5 MeV was achieved that is twice as large of the resolution of high-precision Si-based detectors prepared on specialized technology. The maximum signal amplitude of 4H-SiC - detectors corresponding to the average electron-hole pair generation energy was found to be 7.70 eV.

Abstract: The effect of gamma-ray and neutron irradiation on recombination current, injection electroluminescense and the value of the lifetime of nonequilibrium carriers for 4H-SiC pn structures was investigated. The irradiation was carried out with gamma-ray (dose 5x106 rad) and 1 MeV neutrons in the doses range from 1.2x1014 cm-2 to 6.24x1014 cm-2. Neutron irradiation with a dose 1.2x1014 cm-2 increased the recombination current, decreased the lifetime for deep-level recombination in the space charge region and decreased the intensity of the edge injection electroluminescense (hnmax » 3.16 eV) by 1.5-2 orders of magnitude; the neutron irradiation with high dose (6.24x1014 cm-2) resulted in increase of the recombination current up to 2 orders of magnitude and decrease of lifetime at least up to 2 orders of magnitude. Gamma-ray irradiation and annealing at temperatures in the range 350-650 K left the recombination current and lifetime practically unchanged.

Abstract: High impedance silicon carbide power RF transistors are reported, which use the technology of Lateral Epitaxy Metal-Semiconductor FET (LEMES). The LEMES transistor utilizes a heavily doped buried depletion stopper to increase output impedance and breakdown voltage and to eliminate undesirable hot-carrier trapping effects. A power density of 2-3 W/mm at 2 GHz is routinely achieved resulting in a total output power of 10W for packaged components. The value of input and output impedance is around 50 Ohms for a frequency of around 2 GHz.

Abstract: The influence of the irradiation with neutrons, Kr+ (245 MeV) and Bi+ (710 MeV) ions on the optical and electrical properties of high-resistivity, high-purity 4H-SiC epitaxial layers grown by chemical vapor deposition was investigated using photoluminescence and deep-level transient spectroscopy. Electrical characteristics were studied using Al and Cr Schottky barriers as well as p+-n-n+ diodes fabricated by Al ion implantation on this epitaxial layers. It was found that both "light" neutrons and high energy heavy ions introduced identical defect centers in 4H-SiC. So, even at extremely high density of the ionization energy of 34 keV/nm, typical for Bi+ ion bombardment, damage structure formation in SiC single crystal is governed by energy loss in elastic collisions.