High Purity Semi-Insulating 4H-SiC Epitaxial Layers by Defect-Competition Epitaxy: Controlling Si Vacancies

Chandrashekhar, M. V. S.; Chowdhury, Iftekhar; Kaminski, P.; Kozłowski, Roman; Klein, P. B.; Sudarshan, Tangali S.

doi:10.1143/apex.5.025502

Cited by 18 publications

(12 citation statements)

References 22 publications

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“…All measurements were performed on commercially available high-purity semi-insulating 4H-SiC diced wafers purchased from Cree [32], and using a scanning ODMR microscopy setup. Similar wafers have been used in other studies, with measured defect concentrations of N, VV, V Si all in the order of 10 14 − 10 16 cm −3 [32,46,47]. For the implanted sample, a high energy carbon implant ([ 12 C] = 10 13 cm −2 , 190 keV, 900 • C anneal for 40 mn) was used, resulting in a calculated (SRIM software) 500 nm thick layer of divacancies.…”

Section: Samplesmentioning

confidence: 99%

Optical charge state control of spin defects in 4H-SiC

et al. 2017

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Defects in silicon carbide (SiC) have emerged as a favorable platform for optically active spin-based quantum technologies. Spin qubits exist in specific charge states of these defects, where the ability to control these states can provide enhanced spin-dependent readout and long-term charge stability. We investigate this charge state control for two major spin qubits in 4H-SiC, the divacancy and silicon vacancy, obtaining bidirectional optical charge conversion between the bright and dark states of these defects. We measure increased photoluminescence from divacancy ensembles by up to three orders of magnitude using near-ultraviolet excitation, depending on the substrate, and without degrading the electron spin coherence time. This charge conversion remains stable for hours at cryogenic temperatures, allowing spatial and persistent patterning of the charge state populations. We develop a comprehensive model of the defects and optical processes involved, offering a strong basis to improve material design and to develop quantum applications in SiC.

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Section: Samplesmentioning

confidence: 99%

Optical charge state control of spin defects in 4H-SiC

et al. 2017

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“…5,6 At present, the standard off-axis angle of commercially available SiC substrates is lowered to 4…”

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confidence: 99%

Study of Surface Morphology, Impurity Incorporation and Defect Generation during Homoepitaxial Growth of 4H-SiC Using Dichlorosilane

Song

Chandrashekhar

Sudarshan

2014

ECS J. Solid State Sci. Technol.

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The growth of 4 • off-axis 4H-SiC epilayers by chemical vapor deposition is studied using dichlorosilane as the Si precursor in a chimney reactor. The unintentional and intentional nitrogen doping at various C/Si ratios and N 2 flow rates are investigated. The C/Si ratio has a significant influence on the growth rate, surface morphology, conversion of basal plane dislocations (BPDs), and generation of other defects (e.g., in-growth stacking faults and morphological defects). Addition of N 2 has no obvious influence on growth rate and BPD conversion. It is preferable to grow high quality n + epilayers at a C/Si ratio in the range of 1.3-1.8 along with the addition of a suitable amount of N 2 in consideration of high growth rate, good surface morphology, and low defect density. In this case, the conversion ratio of BPDs to threading edge dislocations is greater than 99.8% regardless of N 2 addition. Therefore >99.8% substrate BPDs can be buried in an n + buffer layer, which is beneficial to SiC bipolar power devices. No special treatment prior to, during or after the epigrowth is necessary. The epilayers with doping concentration all the way from p − (∼1e15 cm −3 ) to semi-insulating, then to n + (∼1e18 cm −3 ), can be achieved, giving a great range of flexibility in growth using dichlorosilane precursor. Further optimization of in-situ etching and growth conditions to eliminate step bunching has also been suggested. 4H-silicon carbide (4H-SiC) is a promising wide bandgap material for high power electronic devices, owing to its unique thermal and electrical properties such as high breakdown field, high thermal conductivity, and high electron saturation velocity.1,2 Chemical vapor deposition (CVD) is a well-developed technique adopted in semiconductor industry to produce high purity and high quality thin films.3 Homoepitaxial growth of SiC via the CVD technique is one of the key steps in the fabrication of high performance SiC devices. Currently, chloride-based CVD has attracted much interest to potentially replace the traditional silane based CVD for SiC epitaxial growth to reduce the Si droplet formation at high growth rates, because of the higher bonding energy of Si-Cl (400 kJ/mol) than SiSi (226 kJ/mol).4 Dichlorosilane (SiH 2 Cl 2 , DCS) is a gas (boiling point: 8.2• C) at room temperature. It has been demonstrated that using DCS and propane (C 3 H 8 ) as the precursors, high crystalline quality 8• off-axis SiC epilayers were achieved at a high growth rate (up to 100 μm/h). 5,6 At present, the standard off-axis angle of commercially available SiC substrates is lowered to 4• to reduce the material loss during substrate preparation from the crystal boules.Step-bunching is a typical surface feature of the epilayers grown on 4• off-axis substrates, resulting in increase in surface roughness. 7Morphological defects, specifically the triangular defects and inverted pyramids, are prone to be generated in epigrowth on low off-axis angle substrates. 8 Hence, determination of optimized growth conditions to produce SiC ...

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“…Dopant compensation leads to semi-insulating material characteristics by pinning the Fermi level near the mid bandgap. Other methods, such as defect competition epitaxy, have also been used to achieve semi-insulating 4H-SiC [24]. In this method, C/Si ratio is varied to reduce the incorporation of nitrogen, while creating silicon or carbon vacancies.…”

Section: A2 Impurity Compensationmentioning

confidence: 99%

Performance Modeling of Silicon Carbide Photoconductive Switches for High-Power and High-Frequency Applications

Rakheja

Huang

Hau‐Riege

et al. 2020

IEEE J. Electron Devices Soc.

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In this article, we focus on the physical modeling of the nonlinear operation of intrinsic photoconductive semiconductor switches (PCSS) based on 4H-SiC using coupled electrical and optical simulations to provide performance bounds of the switch as a function of material and geometry parameters, as well as applied bias. We also conduct a full design-space exploration to identify the optimal operating and design conditions to maximize the compound metric f op P out , where f op is the maximum operating frequency, and P out is the maximum output power the switch can provide. We quantify that a 10-μm long and 5-μm thick 4H-SiC PCSS can deliver output power density greater than 2W/mm at 150 GHz when triggered by a 0.325-μm laser with intensity of 3 kW/cm 2 . The output power density can be significantly enhanced by increasing the optical generation rate as well as by using thicker SiC to improve its absorption characteristics. A brief discussion of signal distortion and electrostatic screening effects at high optical bias is included. Finally, we present an analytic model of charge cloud propagation and the frequency of operation based on the physics, material parameters, and geometry of the PCSS. The model accurately captures f op of 4H-SiC PCSS over a broad range of laser spot size, device length, and electrical bias applied at the contacts.INDEX TERMS Optical triggering, wide bandgap, intrinsic photoconductivity, high-field electron transport, high-frequency operation, compact modeling, performance tradeoff.

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High Purity Semi-Insulating 4H-SiC Epitaxial Layers by Defect-Competition Epitaxy: Controlling Si Vacancies

Abstract: Thick, high-purity semi-insulating (SI)homoepitaxial layers on Si-face 4H-SiC weregrownsystematically, with resistivity 10

Cited by 18 publications

References 22 publications

Optical charge state control of spin defects in 4H-SiC

Optical charge state control of spin defects in 4H-SiC

Study of Surface Morphology, Impurity Incorporation and Defect Generation during Homoepitaxial Growth of 4H-SiC Using Dichlorosilane

Performance Modeling of Silicon Carbide Photoconductive Switches for High-Power and High-Frequency Applications

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