Photoelectrochemical etching of n-type 4H silicon carbide

Shishkin, Y.; Choyke, W. J.; Devaty, Robert P.

doi:10.1063/1.1768612

Cited by 75 publications

(80 citation statements)

References 32 publications

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“…With a lattice constant and thermal expansion coefficient close to those of GaN, SiC is also an attractive substrate for group III nitride-based optoelectronic devices, such as blue lightemitting diodes and diode lasers [2]. Furthermore, extensive work is under way to apply porous SiC in biomedical technology, such as protein dialysis and bone tissue engineering, and in fuel cell technology [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Photoelectrochemistry of 4H–SiC in KOH solutions

Dorp

Kelly

2007

Journal of Electroanalytical Chemistry

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The photoelectrochemical oxidation of n-type 4H-SiC in KOH solution shows surprising features. While a limiting anodic photocurrent is observed at low light intensity, the semiconductor passivates at high intensity. The photocurrent corresponding to the passivation peak increases linearly with photon flux but decreases when mass transport in the system is enhanced. Characteristic current oscillations are observed. Possible reasons for these results are considered, as is the use of photoanodic etching for practical applications.

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Section: Introductionmentioning

confidence: 99%

Photoelectrochemistry of 4H–SiC in KOH solutions

Dorp

Kelly

2007

Journal of Electroanalytical Chemistry

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“…Among them, the first two are nominally terminated with Si atoms, and the last is terminated with C atoms. 25,30 The densities of Si atoms are 6.09 nm −2 on (0001) Si face and 5.71 nm −2 on {1102} planes, respectively. We can reasonably conclude that the etching rate is close to each other for the Si-terminated (0001) and {1102} planes.…”

Section: Resultsmentioning

confidence: 99%

Crystal structure induced residue formation on 4H-SiC by reactive ion etching

et al. 2016

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The (0001¯) C face of 4H-SiC wafer was etched by reactive ion etching in SF6/O2 plasma. The effect of etching parameters, such as work pressure, SF6:O2 ratio and etching time, on the residue formation were systematically investigated. The residue morphologies were observed by scanning electron microscopy and atomic force microscopy, respectively. The residues have spike shape and their facets are defined as {11¯02¯} crystal planes. They are formed at beginning of the etching and no new spikes are generated as prolonging etching time. Both work pressure and SF6:O2 ratio play significant role in the spike formation. The residues can be eliminated completely by increasing the SF6:O2 ratio and work pressure. On the basis of experimental results and of 4H-SiC crystal structure, the spike formation model is proposed.

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“…As stated in literature, the dissolution of SiC is a two-step process, involving the oxidation of SiC and subsequent dissolution of the oxide with HF. 11 It has been shown that the electrolytic oxidation of SiC generates an amorphous oxide layer on its surface, which is permeable for electrolyte solutions. 26 An amorphous layer has also been found on the surface of porous SiC prepared with PECE.…”

Section: Discussionmentioning

confidence: 99%

“…17 Porous layers prepared with constant voltage conditions showed a decreasing porosity with depth. 11 These observations are cumbersome when a constant degree of porosity is required, such as in the preparation of optical filters 18 or membranes for biological applications. 19 This work aims to create a process serving as technological basis for the preparation of porous SiC layers that can be used within e.g.…”

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confidence: 99%

“…10 In contrast to electrochemical etching of Si, photo-electrochemical etching (PECE) of SiC in HF based etching solutions is a comparably challenging task and hence, only a limited number of publications exist. 11,12 Some authors report a skin layer on top of the porous structure, which exhibits only a few pores with diameters in the nm range. 13,14 This skin layer is followed by a cap layer which shows an irregular porous structure.…”

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Stacked Layers of Different Porosity in 4H SiC Substrates Applying a Photoelectrochemical Approach

Leitgeb

Zellner

Hufnagl

et al. 2017

J. Electrochem. Soc.

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Porous 4H-SiC layers were prepared from monocrystalline samples applying photo-electrochemical etching in hydrofluoric acid. The influence of both current and voltage controlled mode during photo-electrochemical porosification was investigated. It was found that the resulting degree of porosity, the homogeneity in porosity as well as the pore morphology mainly depend on the applied voltage, whereas the current level has an almost negligible impact on these important parameters. Based on these results, it is proposed that the formation of porous SiC during photo-electrochemical etching can be described by fractal growth. Finally the gathered knowledge allowed to detach the porous 4H-SiC layers, which comprised several sub-layers of alternating degree of porosity, from the 4H-SiC substrate. Such layers of tailored porosity are key components for several advanced device concepts such as optical filters or membranes for biological applications. A common method to prepare porous Si is electrochemical etching in HF based solutions.1 There are numerous application scenarios of porous Si, such as electrode material in super-capacitors, 2 as sacrificial layer in the production of MEMS devices 3 or as optical filters in bio-or vapor-sensors. 4,5 In the last application scenario, a stacked layer of porous silicon is electrochemically etched into a silicon wafer. The individual porous layers of the stack show alternating degrees of porosity and thus have a different index of refraction. This results in a wavelength selective reflection of optical light.6 Undoubtedly, porous Si is a well-established material for future micro-or nanomachined device architectures, but it shows a poor chemical stability when exposed to e.g. air at higher temperatures or alkaline electrolytes. 7,8 Therefore it has to be covered with a dense protective layer when operation in harsh or biological environments is targeted.9 This drawback encourages research devoted to other porous materials that can be used instead of porous Si without a surface protection. A promising candidate is porous SiC prepared from single crystalline wafers because it shows a higher chemical stability than silicon.10 In contrast to electrochemical etching of Si, photo-electrochemical etching (PECE) of SiC in HF based etching solutions is a comparably challenging task and hence, only a limited number of publications exist.11,12 Some authors report a skin layer on top of the porous structure, which exhibits only a few pores with diameters in the nm range.13,14 This skin layer is followed by a cap layer which shows an irregular porous structure. 15 This problem has been addressed recently by a combination of metal assisted photochemical etching with PECE. 16 Metal assisted photochemical etching (MAPCE) can be utilized to generate a layer in the μm range prior to PECE. The pore tips of this porous layer provide initiation sites for PECE. Thus, neither a skin nor a cap layer are observed.Furthermore some authors report about an increased porosity at the bottom of the porous laye...

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Photoelectrochemical etching of n-type 4H silicon carbide

Cited by 75 publications

References 32 publications

Photoelectrochemistry of 4H–SiC in KOH solutions

Photoelectrochemistry of 4H–SiC in KOH solutions

Crystal structure induced residue formation on 4H-SiC by reactive ion etching

Stacked Layers of Different Porosity in 4H SiC Substrates Applying a Photoelectrochemical Approach

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