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![Distribution of NB in 4H-SiC<B> crystal after diffusion at 1300°C, measured by spreading resistance method on the angle polished sample [38].](publication/323462801/figure/fig2/AS:1086473164075055@1636046796494/Distribution-of-NB-in-4H-SiCB-crystal-after-diffusion-at-1300C-measured-by-spreading.jpg)
Distribution of NB in 4H-SiC<B> crystal after diffusion at 1300°C, measured by spreading resistance method on the angle polished sample [38].
Source publication
Novel method of boron diffusion at low temperatures between 1150 and 1300°C is used for the formation of both p - i SiC junction and i -region in one technological process. As the junction formation conditions in this method are essentially different from those in the conventional diffusion (low temperatures and process of diffusion are accompanied...
Citations
... The optimization of applied bias current and device design parameters are basically required for getting best performance from the designed devices at around 94 GHz centre frequency. Cubic/hexagonal n-SiC is doped using nitrogen/ phosphorus and p-SiC is doped using boron/beryllium/ aluminium/gallium (Feng 2003;Dmitriev et al. 1995;Atabaev et al. 2018). The doping concentration of the p ?? cap layer (* 5 9 10 25 m -3 ), p ? layer (10 25 m -3 ), n buffer layer (3 9 10 22 m -3) and n ?? region (8 9 10 25 m -3 ) are optimized through several computer run (Zekentes et al. 2005;Camara et al. 2008). ...
... As far as authors' knowledge is concerned, no reports on experimental findings are available on SiC pin switches at around 94 GHz window frequencies, therefore, the W-band analytical data could not be compared with experimental observations. However, experimental validation at W-band region could be done through following process steps: Si(100) and SiC are the preferred substrate materials for 3C-SiC and 4H/6H-SiC epilayer growth (Atabaev et al. 2018;Zekentes et al. 2005;. SiC epi-wafer as described and analysed in section-3, would be obtained from Cree Inc. Durham, NC, USA. ...
A modified quantum drift-diffusion (QDD) model is developed for non-linear analysis of SiC (4H, 6H and 3C polytypes) pin semiconductor diodes at W-band frequency regime. Effects of incorporation of a buffer layer (n-type), in between substrate and low doped active region of the hexagonal (4H and 6H) pin (p⁺⁺-p⁺-n⁻-n-n⁺⁺) vertical mesa structure is thoroughly studied in this paper for the improvement of MM-wave performance of the single device. Also, a thin layer of Ge has been introduced in between Si substrate and n⁺ cubic-SiC layer in 3C-SiC pin-device for minimising the lattice mismatch issue in between Si/3C-SiC interface. The comprehensive analysis establish that the forward characteristics, reverse recovery time (1 ns) and breakdown voltage (171 Volt) in case of 4H-SiC device are quite good in comparison to its cubic (3C) and other hexagonal (6H) counterparts, however, the switching characteristics of 3C-SiC pin diode array is comparatively better than its hexagonal counterparts. This observation could be explained in terms of lowest series resistance in 3C-SiC based single pin device that has been achieved by incorporating Ge layer in mesa structure. The authors have made a comparative analysis among SPST, SPDT and SPMT pin switches made up with 4H, 6H and 3C-SiC poly-types. At 94 GHz, W-band central frequency, series resistance in 4H-SiC single device is 0.59 Ω, whereas, the same is much lower (0.27 Ω) in case of 3C-SiC. Insertion loss and isolation in 3C-SiC pin array of switches are found to be 0.18 dB and 38 dB (SPST switch), 0.19 dB and 67 dB (SPDT switch), 0.20 dB and 90 dB (SPMT shunt type switching array) and 0.23 dB and 74 dB (SPMT series-shunt type switching array). This newly proposed QDD model validation is done through comparative studies between experiment and analytical results for 4H-SiC SPST switches in low-frequency Microwave region. The validated QDD model, coupled with PSpice and Comsol Multi-physics simulator, then used for designing of the W-band devices and corresponding switches. However, as far as author’s knowledge is concerned, no experiment is yet done with SiC pin diodes at W-band frequencies, in literature for comparison. From simulation point of view also such an extensive study on hexagonal and cubic SiC pin diode switches at W-band region has not yet been done by any other researcher group. This paper, for the first time, establishes the feasibility and potentiality of IV-IV group semiconductor based pin (p⁺⁺-p⁺-n⁻-n-n⁺⁺) switches for W-band applications. Comparative analysis also reveals that 3C-SiC based shunt type pin (p⁺⁺-p⁺-n⁻-n-n⁺⁺) SPMT switches are the best for MMW-communication systems. Thermal modelling of the designed devices are also compared and reported in this paper. The quasi-3D thermal analysis is done to optimize the mesa and heat-sink diameter/dimensions so as to minimize the thermal runaway issues. The results may further be used for developing low-cost and fast semiconductor switches for potential application in THz communication systems.
... The photo-energy conversation at shorter wavelength region of EMspectra is complicated and expensive, so dark current should be low as much as possible in such applications. Substantial research work have been done for studying the photo-electric properties of Si, GaAs, GaN, SiC based single pin photo-sensors in terms of photo generation rate, photo-current, responsivity and quantum efficiency (Cha and Sandvik 2008;Campbell and Chang 1967;Muench et al. 1976;Atabaev and Juraev 2018). Epilayer growth technology of Wide Bandgap (WBG) SiC and GaN is maturing daily; also matching substrates are available now in market for developing almost crack free high quality epilayer of SiC and GaN for applications in visible wavelength region. ...
... To the best of authors' knowledge, no experimental reports are available on Si/SiC pin sensors at visible wavelength, therefore, the simulation data could not be compared with those of experimental results. However, experimental validation could be done through following process steps: SiC is the preferred substrate material for 4H epilayer growth (Atabaev andJuraev 2018, Zekentes andCamara 2005;Mukherjee and Mazumder 2010). SiC epiwafer (n ? ...
Photo-sensors are integral part of different bio-medical diagnostic equipment. Each type of bio-molecules possess unique spectral fingerprint in visible wavelength region of electro-magnetic spectrum. Now-a-days, the enhancement of quantum-efficiency and photo-responsivity of such bio-medical opto-sensors, for accurate identification of virus/anti-bodies in blood by optical means, is a big challenge to medical-device Engineers. The authors have addressed this issue in this research paper by proposing a novel structure of asymmetrical Si/4H-SiC super-lattice pin diode array for the development of high-sensitive visible light (300–800 nm) sensor on native substrate. The simulation experiment is carried out by developing a generalized large-signal quantum modified drift–diffusion simulator incorporating three different modes of carrier generation-recombination under light and dark conditions: avalanching, tunneling and photo-irradiation. The validity of the model has been established by comparing the simulation results with those of experimental observations. A good agreement between theory and experiment, under similar biasing conditions, establishes the validity of the developed model. The characteristics analysis depicts that the quantum efficiency of the designed single photo-sensor is ~ 65% within 400–700 nm wavelength region, whereas, the same enhances to nearly ~ 90% with a 3 × 3 photo-sensor array based on asymmetrical super-lattice single pin devices. In visible wavelength region, the simulated photo-sensors (both single and array) have demonstrated significant photo responsivity. The photo-responsivity values, at 500 nm wavelength of incident radiation, are observed to be 0.65 A/W for a single photo-diode and 0.85 A/W for a 3 × 3 combination of photo-diode array. This clearly establishes the potentiality of the asymmetrical super-lattice pin-array as a visible photo-sensor for future application in developing medical instruments. A comparative analysis of Si and Si/4H-SiC asymmetrical super-lattice photo-sensors establishes the superiority of the later as a high-sensitive visible light-sensor in terms of better photo-responsivity and quantum efficiency. To the best of authors’ knowledge, this is the first report on Si/4H-SiC super-lattice pin photo-sensor array in the visible range of optical irradiation. The experimental feasibility of the device and a proposed circuit for future bio-medical implementation are also incorporated in the present research-paper for further development.
... We have developed a new low-temperature method for shallow impurities diffusion in silicon carbide at temperatures of 1150-1300°C. e method is described in details in publications [7][8][9][10][11] and patented in Uzbekistan and the USA [12,13]. A significant decrease in temperature is due to the fact that diffusion occurs in the flow of carbon and silicon vacancies. ...
... Advantages of low-temperature di usion are as follows: shallow impurity concentration of up to 10 20 cm −3 (unreachable for conventional thermal di usion and ion implantation technique), and fast switching time of <10 ns of p-i-n SiC diodes fabricated by this method (>20 ns for diodes fabricated by conventional technology) [10,11]. ...
Optical absorption of p-n-4H-SiC structures doped with boron and aluminum by low-temperature diffusion was studied for the first time. Diffusion of impurities was performed from aluminum-silicate and boron-silicate films (sources) fabricated by various methods. In the spectral dependences of optical absorption at room temperature, bands associated with transitions from impurity levels, as well as absorption bands associated with defects of the vacancy nature, were observed. -e level of absorption in the samples was used to estimate concentration of defects. It was shown that the use of sources of impurity atoms created by using
boron and aluminum chlorides allows one to reduce the concentration of vacancy defects.
Für die Herstellung von Leistungshalbleiterbauelementen sind reproduzierbare, niederohmige Kontakte elementar. Hierzu ist es notwendig, dass die zugrundeliegenden Bildungsmechanismen verstanden sind und darauf aufbauend das elektrische Verhalten der Kontakte modelliert werden kann. Im Rahmen dieser Arbeit wurden Ti/Al-basierte ohmsche Kontakte auf p-dotiertem 4H-SiC realisiert, anschließend elektrisch charakterisiert und strukturell analysiert und aufbauend auf den Ergebnissen ein numerisches Simulationsmodell entwickelt. Zur Untersuchung des Einflusses von Prozessvariationen auf das ohmsche Verhalten wurden unterschiedliche Probensätze hergestellt. Auf jedem Probensatz wurden Transferlängenmethode (engl. Transfer Length Method) (TLM) Strukturen realisiert, welche es erlauben, den hergestellten ohmschen Kontakt und die darunterliegende Halbleiterschicht elektrisch zu charakterisieren. Hierdurch konnte der Kontaktwiderstand R_C bzw. der spezifische Kontaktwiderstand rho_C als Kennwert für den ohmschen Kontakt und der Schichtwiderstand R_sh als Kennwert für die zugehörige Halbleiterschicht ermittelt werden. Die elektrische Charakterisierung der hergestellten Proben zeigte, dass alle Proben ohmsches Verhalten aufwiesen. Weiterhin zeigten die Ergebnisse, dass der Schichtwiderstand des Halbleitergebiets der hergestellten Proben signifikant höher war, als aus der Theorie zu erwarten gewesen wäre. Diese Abweichung konnte mit der Kompensation der freien Löcher durch vorhandene Elektronen bzw. durch implantationsbedingte Kompensationszentren erklärt werden. Zur Beschreibung der Kompensation wurde in dem, im Rahmen dieser Arbeit entwickelten, Simulationsmodell der Kompensationsgrad f_comp verwendet. Bezüglich des spezifischen Kontaktwiderstands unterschieden sich die hergestellten Probensätze jedoch deutlich, abhängig davon, ob der abgeschiedene Ti/Al-Metallstapel ein umgebendes Passivierungsoxid berührte. Bei den Prozessvarianten mit Abstand zwischen dem abgeschiedenen Ti/Al-Metallstapel und dem umgebenden Passivierungsoxid wurden, ausgehend von den nominellen Kontaktflächen, effektive, spezifische Kontaktwiderstände von 0,5 mOhmcm² bei Raumtemperatur erreicht. Dieser Wert entspricht den, aus der Literatur bekannten, spezifischen Kontaktwiderständen für niederohmige Kontakte. Die Prozessvarianten ohne Abstand wiesen, ausgehend von den nominellen Kontaktflächen, einen effektiven, spezifischen Kontaktwiderstand von 700 mOhmcm² bei Raumtemperatur auf. Dieser sehr große Unterschied konnte durch strukturelle Analysen des ohmschen Kontaktbereichs auf eine Reaktion des Al mit dem umgebenden SiO2 zurückgeführt werden. Hierdurch wurde die Al-Konzentration in dem Ti/Al-Metallstapel signifikant verringert, was zu einem unvollständigen Aufwachsen von Ti3SiC2 an der 4H-SiC-Oberfläche und somit zu einer unvollständigen ohmschen Kontaktbildung führte. Aus dieser unvollständigen Kontaktbildung resultiert eine effektive Reduktion der ohmschen Kontaktfläche und somit eine Erhöhung des Kontaktwiderstands. Die Reduktion der Kontaktfläche wurde mit Hilfe des Flächenfaktors f_area im numerischen Simulationsmodell beschrieben. Weiterhin konnten aus dem temperaturabhängigen Verhalten des spezifischen Kontaktwiderstands die Schottkybarrierenhöhen phi_B aller Probensätze ermittelt werden. Diese zeigten einen Anstieg der Schottkybarrierenhöhe mit steigender Al-Konzentration an der 4H-SiC-Oberfläche. Vergleicht man diese Ergebnisse mit aus der Literatur bekannten Werten, zeigt sich übereinstimmendes Verhalten. Dieses Verhalten widerspricht allerdings dem, aus den physikalischen Grundlagen bekannten Zusammenhang zwischen Schottkybarrierenhöhe und Dotierstoffkonzentration, da die Schottkybarrierenhöhe aufgrund des Schottky-Effekts mit steigender Dotierung fallen sollte. Dieser Widerspruch wurde mit der Hypothese, dass sich die Al-Konzentration an der 4H-SiC-Oberfläche während der ohmschen Kontaktbildung erhöht, im Rahmen dieser Arbeit erstmals erklärt. Da die Erhöhung der Al-Konzentration durch die Eindiffusion beziehungsweise Ansammlung von Al in die 4H-SiC-Oberfläche entstanden ist, wurde zur Beschreibung dieser Erhöhung eine Gaußsche Normalverteilung mit der Dosis der eindiffundierten Al-Konzentration N_Al,Dosis und der zugehörigen Diffusionslänge L_Al,Diff verwendet. Unter Verwendung der Parameter f_comp, f_area, N_Al,Dosis und L_Al,Diff wurde ein numerisches Simulationsmodell in Sentaurus TCAD implementiert. Mit dessen Hilfe konnte das elektrische Verhalten der hergestellten Probensätze temperaturabhängig mit sehr guter Genauigkeit simuliert werden. Zur Verifizierung des numerischen Simulationsmodells wurden an der 4H-SiC-Oberfläche Sekundärionen-Massenspektrometrie (SIMS) Analysen mit einer Tiefenauflösung im Nanometerbereich durchgeführt. Diese Analysen konnten einen signifikanten Anstieg der Al-Konzentration an der 4H-SiC-Oberfläche in den ersten Nanometern nachweisen und somit die im Rahmen dieser Arbeit aufgestellte Hypothese bestätigen. Somit konnte in dieser Arbeit gezeigt werden, dass sich die Al-Konzentration an der 4HSiC-Oberfläche während der ohmschen Kontaktbildung signifikant erhöht und diese Erhöhung entscheidend ist für die Bildung von ohmschen Kontakten auf p-dotiertem 4H-SiC bei der Verwendung eines Ti/Al-basierten Metallstapels.
A study has been made of the activation energy of the conductance of a p–n-4H-SiC 〈Al〉 structure created through the doping of silicon carbide with aluminum. The doping was implemented by a novel method of low-temperature diffusion, in which the diffusion of aluminum in silicon carbide is stimulated by a carbon- and silicon-vacancy flux produced by the oxidation of the silicon surface.
The influence of the high temperature annealing on differently implanted Al profiles was investigated by SIMS measurements. Depending on the implanted dose and also depending on the local concentration a significant diffusion of the implanted Al was observed. Based on this results at least two necessary conditions of Al diffusion during high temperature annealing could be determined.
For the first time, authors have designed and characterized Si/4H-SiC asymmetrical super-lattice p++-p+-n-- n-n++ type pin switch in D and Y-band communication systems by incorporating the Quantum-Modified Drift-Diffusion (QDD) model. It has been observed that the RF series resistance of the exotic super-lattice p++-p+-n-- n-n++ type pin device operating at around 140GHz (D-band) and 220GHz (Y-band) frequency regime reduces due to the incorporation of QDD model. The designed super-lattice pin devices are considered as SPD1 for D-band and SPD2 for Y-band. The proposed SPD2 devices offers the faster reverse recovery time (∼0.11ns) and low forward RF-series resistances (0.78Ω) compared to its SPD1 counterpart. The SPD2 shunt SPST switch also offers low insertion loss (0.085dB at 140GHz & 0.097dB at 220GHz) and high isolation (49dB at 140GHz and 30dB at 220GHz). An excellent agreement between experiment and theory establishes the advantage of the proposed model over the others.
