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X-band Silicon Carbide IMPATT Oscillator Konstantin V. Vassilevski#, Alexandr V. Zorenko1, Konstantinos Zekentes2 Ioffe Institute, St. Petersburg, 194021, Russian Federation 1 State Scientific & Research Institute “Orion”, Kyiv, 03057, Ukraine 2 Microelectronics Research Group, FORTH, Heraklion, 711 10, Greece ABSTRACT Pulsed X-band (8.2 - 12.4 GHz) IMPATT oscillators have been fabricated and characterized. They utilized 4H-SiC diodes with single drift p+-n-n+ structures and avalanche breakdown voltages of about 290 V. The microwave oscillations appeared at a threshold current of 0.3 A. The maximum measured output power was about 300 mW at input pulse current of 0.35 A and pulse duration of 40 ns. INTRODUCTION IMPact-ionisation Avalanche Transit-Time (IMPATT) diodes were proposed by Read for microwave power generation in 1958 [1] and demonstrated by Tager in 1959 [2]. In 1973, Keyes considered silicon carbide (SiC) as a promising material for fabrication of this device [3]. Quite accurate analytical estimations of SiC performance for IMPATT diode fabrication became available after the saturated drift velocity of the electrons (vS) in 6H-SiC, of about 2⋅107cm/s, had been measured [4]. As a result, it was concluded that SiC IMPATT diodes should have 30 - 50 times higher output power and about 10 times higher theoretical limit of oscillation frequency comparing with Si and GaAs diodes [5]. Also, it was concluded that the polytype 4H-SiC is most convenient for IMPATT diode fabrication due to the high and nearly isotropic electron mobility [6]. A number of numerical simulations [7, 8] confirmed these estimations, but they did not give enough information to perform an accurate design of SiC IMPATT diodes, namely to calculate the optimal operating frequency of the structure with given doping profile. Indeed, the most important material parameter used in these numerical calculations, namely vS, was not determined accurately. It was measured at E < 2×105 V/cm in the directions parallel [9] and perpendicular [4, 10] to the c-axis, while the avalanche breakdown field in SiC is much higher. Some experimental attempts to fabricate SiC diodes capable to operate at high avalanche current densities were performed also. 6H-SiC [11] and 4H-SiC [12] p+-n diodes with breakdown voltages about 140 V operating at pulsed avalanche current densities up to jA ≅ 60 kA/cm2 were demonstrated, but no microwave characterizations were performed, apparently due to the high resistivity of the contacts used for fabrication of these diodes. Recently, significant progress has been achieved in 4H-SiC growth, device processing and material characterization. First of all, high quality epitaxial layers of 4H-SiC with excellent tolerance in doping level and layers thickness became commercially available [13]. Also, the key device processing problem, formation of low resistance ohmic contact to p-doped 4H-SiC, was resolved. Ohmic contacts with RC < 10-4Ω⋅cm2 were developed [14, 15]. Device processing compatibility of these contacts was proved by their use fo