High doped MBE Si p–n and n–n heterojunction diodes on 4H-SiC (original) (raw)
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Journal of Applied Physics
In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy ͑MBE͒ deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics ͑n Ͻ 1.05͒, low on resistance and good reverse characteristics. Current-voltage ͑I-V͒ measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height ͑SBH͒ due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.
Further studies of N doped a-SiC:H films deposited by PECVD and annealed by pulse electron beam
Thin Solid Films, 2004
The properties of nitrogen-doped amorphous SiC films irradiated by pulse electron beams are presented. The RBS results showed that the concentrations of Si, C and N in the films are practically the same. The concentration of hydrogen was determined by the ERD method and the value is approximately 20 at.%. The films contain a small amount of oxygen. IR results showed the presence of Si-C, Si-H, C-H and Si-O bonds. The I-V characteristics of diodes made of irradiated SiC films grown on silicon substrates were investigated. The results showed that the film conductivity increased by about two orders of magnitude as nitrogen fraction was increased from 10 to 14 at.%. The film conductivity was enhanced by about one order of magnitude as a result of twofold increase of pulse electron beam irradiation.
Journal of Electronic Materials, 2005
Selective nitrogen doping of 4H-SiC by epitaxial growth using TaC as the hightemperature mask has been demonstrated. Nomarski optical microscopy and scanning electron microscopy (SEM) were used to characterize selective growth of SiC. In addition, 250-µm, square-shaped, p-n junction diodes by selective n-type epitaxial growth on a p-type epilayer were fabricated. The refilled fingers with different width were designed to vary the periphery/area (P/A) ratio. The effects of P/A ratio on the current-voltage (J-V) characteristics have been investigated. The ideality factor extracted from J-V characteristics is Ϸ2 at a temperature range of 25-275°C, which indicates that the Shockley-Read-Hall recombination is the dominant mechanism in the conduction region. The reverse leakage current does not show dependence on P/A ratio for trench-refilled diodes. The room-temperature reverse leakage-current density at 100 V is less than 3.5 ϫ 10 Ϫ7 A/cm 2 for all diodes. Also, the reverse leakage current does not increase significantly with temperature up to 275°C. The breakdown voltages measured at room temperature are about 450 V and 400 V for diodes without and with fingers, respectively.
Scientific Reports
This work examines the stability of epitaxial 3C-SiC/Si heterojunctions subjected to heat treatments between 1000 °C and 1300 °C. Because of the potential for silicon carbide in high temperature and harsh environment applications, and the economic advantages of growing the 3C-SiC polytype on large diameter silicon wafers, its stability after high temperature processing is an important consideration. Yet recently, this has been thrown into question by claims that the heterojunction suffers catastrophic degradation at temperatures above 1000 °C. Here we present results showing that the heterojunction maintains excellent diode characteristics following heat treatment up to 1100 °C and while some changes were observed between 1100 °C and 1300 °C, diodes maintained their rectifying characteristics, enabling compatibility with a large range of device fabrication. The parameters of as-grown diodes were J 0 = 1 × 10 −11 A/mm 2 , n = 1.02, and +/−2V rectification ratio of 9 × 10 6. Capacitance and thermal current-voltage analysis was used to characterize the excess current leakage mechanism. The change in diode characteristics depends on diode area, with larger areas (1 mm 2) having reduced rectification ratio while smaller areas (0.04 mm 2) maintained excellent characteristics of J 0 = 2 × 10 −10 A/mm 2 , n = 1.28, and +/−2V ratio of 3 × 10 6. This points to localized defect regions degrading after heat treatment rather than a fundamental issue of the heterojunction.
Silicon dioxide and silicon nitride as a passivation and edge termination for 4H-SiC Schottky diodes
Diamond and Related Materials, 2005
MIS capacitors were fabricated: by thermal oxidation as well as nitridation of silicon carbide (SiC) surface. Their high frequency capacitance-voltage (HF C-V) and current-voltage (I-V) characteristics were measured within the temperature range from 20 8C to 300 8C and 350 8C, respectively. The flat-band voltage, equivalent oxide charge and average interface state density were extracted from the curves. The refractive index of layers was examined by variable angle spectroscopic ellipsometry. Next, Ni/4H-SiC Schottky diodes with passivation and edge termination were fabricated based on results of oxidation process. Their HF C-V and I-V characteristics were measured and then the electrical parameters like ideality factor, on-resistance, Schottky barrier height and saturation current were calculated.
Characterization of n-n Ge/SiC heterojunction diodes
Applied Physics Letters, 2008
In this paper we investigate the physical and electrical properties of germanium deposited on 4H silicon carbide substrates by molecular beam epitaxy. Layers of highly doped and intrinsic germanium were deposited at 300 and 500°C and compared. Current-voltage measurements reveal low turn-on voltages. The intrinsic samples display ideality factors of 1.1 and a reverse leakage current of 9 ϫ 10 −9 A / cm 2 , suggesting a high quality electrical interface. X-ray diffraction analysis reveals the polycrystalline nature of the high-temperature depositions, whereas the low-temperature depositions are amorphous. Atomic force microscopy shows that the low-temperature layers have a rms roughness of 3 nm.
IEEE Transactions on Electron Devices, 1994
AbstructSiCISi heterojunction diodes have been fabricated by two different rapid thermal chemical vapor deposition (RTCVD) processes: a localized self-selective growth and blanket growth. The self-selective growth of crystalline cubic (p) SIC was obtained by propane carbonization of the Si substrate in regions unprotected by an Si02 layer, producing planar diodes. Mesa diodes were fabricated using the blanket growth of polycrystalline p-Sic produced by the decomposition of methylsilane (CH3 SiH3). The SiC/Si heterojunction diodes show good rectifying properties for both device structures. Reverse breakdown voltage of 50 V was obtained with the self-selective Sic& diode. The mesa diodes exhibited even higher breakdown voltages (Vbr) of 150 V and excellent ideality factors of 1.06 at 25°C. The high Vbr and good forward rectifying characteristics indicate that the SiC/Si heterojunction diode represents a promising approach for the fabrication of wide-gap emitter SiC/Si heterojunction bipolar transistors.
A Study of a-Sic/C-Si(n) Isotype Heterojunctions
Active and Passive Electronic Components, 1993
In the present work a study of the electrical properties of heterojunctions between rf sputtered amorphous silicon carbide (a-SiC) thin films and n-type crystalline silicon (c-Si) substrates is reported. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics, as well as the temperature dependence of the current of a-SiC/c-Si(n) heterojunctions were measured. The I-V characteristics of a-SiC/ c-Si(n) heterojunctions exhibit poor rectification properties, with a high reverse current, at higher temperatures (T > 250K), whereas good rectification properties are obtained at lower temperatures (T < 250K). It was found that the a-SiC/c-Si(n) heterojunctions are isotype, suggesting that-the conductivity of a-SiC is n-type. The temperature dependence of the current (from 185K to 320K) showed that the majority carriers of c-Si(n) (i.e. electrons) are transported from c-Si(n) to a-SiC mainly by the thermionic emission mechanism, or by the drift-diffusion mechanism. From ...