Electrochemical Formation of Uniform and Straight Nano-Pore Arrays  on (001) InP Surfaces and Their Photoluminescence Characterizations

Fujikura, Hajime; Liu, Aimin; Hamamatsu, A.; Sato, Taketomo; Hasegawa, Hideki

doi:10.1143/jjap.39.4616

Cited by 63 publications

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“…This behavior can be explained in terms of a quantum-size effect in the InP nanowalls, as similar to the template porous samples. 13 These results indicate that the cathodic decomposition process is very effective for the size tuning of InP nanoporous structures.…”

Section: H154mentioning

confidence: 85%

“…We have recently succeeded in the anodic formation of arrays of straight nanopores on n-InP͑001͒ substrates. [13][14][15] The straightness of pores in the depth direction has been dramatically improved using an HCl-based electrolyte containing a small amount of HNO 3 , resulting in the formation of a high-density array of InP nanowalls with a high aspect ratio. These kinds of unique nanostructures have not been obtainable by other methods.…”

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confidence: 99%

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Electrochemical Formation of Size-Controlled InP Nanostructures Using Anodic and Cathodic Reactions

Sato

Fujino

Hashizume

2007

Electrochem. Solid-State Lett.

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A two-step electrochemical process using anodic and cathodic reactions was developed to form size-controlled nanostructures on InP͑001͒ substrates. After anodic formation of a nanopore array, the cathodic decomposition process was applied to reduce the thickness of InP nanowalls. The etching rate of the nanowalls was extremely small and strongly dependent on the cathodic bias and crystal orientations of the wall surface. Wall thickness could be controlled in the range of 10-30 nm by changing the cathodic bias and processing time. © 2007 The Electrochemical Society. ͓DOI: 10.1149/1.2713662͔ All rights reserved.Manuscript submitted November 9, 2006; revised manuscript received January 10, 2007. Available electronically March 13, 2007. High-density formation of semiconductor nanostructures has recently been intensely researched for applications such as photonic crystals, quantum and optoelectronic devices, and chemical and biochemical sensors. Mainstream approaches to forming semiconductor nanostructures have used conventional methods such as lithography, dry etching, or crystal growth processes. For example, reactive ionbeam etching ͑RIBE͒, molecular beam epitaxy ͑MBE͒, and metallorganic vapor phase epitaxy ͑MOVPE͒ are common techniques for this purpose in the semiconductor community. One possible alternative approach is to apply the electrochemical process to semiconductors. With this process, a wide variety of semiconductor nanostructures can be obtained by modifying the surface using electrochemical anodic and cathodic reactions. The electrochemical process seems to be extremely promising for creating semiconductor nanostructures due to its unique features such as being a lowtemperature process, causing low processing damage, and having a simple process and a low cost.The most well-known application of the electrochemical process is for forming a porous Si structure using the anodic reaction in an HF-based electrolyte.1-3 This has given a visible light-emitting property to Si by modifying the surface. Canham 3 reported that the photoluminescence ͑PL͒ peak obtained from porous Si showed a significant blue shift with reference to the bandgap energy of a bulk Si, showing evidence of quantum confinement in porous structures. Several groups later reported on porous structures made of III-V semiconductor materials such as GaAs, 4,5 GaP, 6,7 InP, [8][9][10]12 Up to the present, various crystal orientations and electrochemical conditions have been investigated on III-V materials to reveal structural properties and their tunability. We have recently succeeded in the anodic formation of arrays of straight nanopores on n-InP͑001͒ substrates. [13][14][15] The straightness of pores in the depth direction has been dramatically improved using an HCl-based electrolyte containing a small amount of HNO 3 , resulting in the formation of a high-density array of InP nanowalls with a high aspect ratio. These kinds of unique nanostructures have not been obtainable by other methods.In this article, we report size-controlled InP nan...

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Section: H154mentioning

confidence: 85%

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confidence: 99%

Electrochemical Formation of Size-Controlled InP Nanostructures Using Anodic and Cathodic Reactions

Sato

Fujino

Hashizume

2007

Electrochem. Solid-State Lett.

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“…We have recently shown that <001>-oriented nanometer sized straight pores, penetrating deep into the semiconductor, can be produced by anodizing (001)-oriented n-type InP in the passive region in a suitable electrolyte [28][29][30]. Such capability of forming <001>-oriented pores seems to be useful for various applications, since (001)-oriented substrates are technologically more important than the (111)-oriented one.…”

Section: 1)formation Of Nanoporesmentioning

confidence: 99%

Electrochemical processes for formation, processing and gate control of III–V semiconductor nanostructures

Hasegawa

Sato

2005

Electrochimica Acta

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This paper reviews recent efforts by authors' group to utilize electrochemical processes for formation, processing and gate control of III-V semiconductor nanostructures. Topics include precise photo anodic and pulsed anodic etching of InP, formation of arrays of <001>-oriented straight nanopores in n-type (001) InP by anodization and their possible applications, and macroscopic and nanometer-scale metal contact formation on GaAs, InP and GaN by a pulsed in-situ electrochemical process, which remarkably reduces Fermi level pinning. All the results indicate that electrochemical processes can achieve unique and important results which the conventional semiconductor technology cannot realize, anticipating their increased importance in future semiconductor nanotechnology and nanoelectronics. Key words:III-V semiconductors, anodic etching, nanopore, electrodeposition, Schottky barrier 1.IntroductionIt is widely recognized that artificial semiconductor nanostructures such as quantum wires (QWRs) and quantum dots(QDs) give rise to new rich functionalities to materials. They produce new quantum state spectra with novel state transitions and linear and non-linear quantum transport phenomena, and open up opportunities for novel quantum devices which control quantum-mechanical behavior of electrons and photons in various sophisticated ways.The standard approach for semiconductor nanostructure formation is to use fine crystal growth techniques such as molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE). To fabricate devices, various standard etching and metal deposition techniques are used together with standard lithography techniques. However, the electrochemical approaches, if it attains sufficiently high controllability at the nanometerscale, seems to be highly useful for nanostructure formation and processing. The expected advantages include: (1) process simplicity and versatility, (2) capability of self-organization, (3) low processing temperature, (4) low process induced damage, (5) precise electrical control and (6) low processing costs.Some well known examples are porous Si formation [1,2] and use of anodized alumina as nanostructure templates for formation of carbon nanotubes [3].The purpose of this paper is to review recent attempts by the authors' group at RCIQE, Hokkaido University, that have been carried out in order to investigate feasibility of utilizing electrochemical processes for nanometer-scale processing and nanostructure formation in III-V semiconductors. Topics discussed in this paper include controlled (1) anodic etching of InP,

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“…[15][16][17] The nanopores were laterally separated by InP nanowalls several tens of nanometers thick and formed in a straight vertical direction greater than several tens of micrometers. We previously reported that pore diameter and wall thickness can be controlled by adjusting the electrochemical anodic and cathodic conditions.…”

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Photoelectrochemical Etching and Removal of the Irregular Top Layer Formed on InP Porous Nanostructures

Sato¹,

Mizohata²

2008

Electrochem. Solid-State Lett.

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A photoelectrochemical ͑PEC͒ process was developed to remove the irregular top layer from InP porous nanostructures. After anodic formation of a nanopore array, the PEC process repeated in the same electrolyte under illumination. The etching rate of the pore surfaces was strongly associated with their structural properties, being greater in the irregular top layer. The irregular top layer was completely removed by monitoring and controlling the anodic photocurrents in the ramped bias mode. © 2008 The Electrochemical Society. ͓DOI: 10.1149/1.2844216͔ All rights reserved.Manuscript received December 11, 2007. Available electronically February 20, 2008 A lot of research has been devoted to producing high-density arrays of nanostructures due to both their applications to future quantum electronic and optoelectronic devices and to downsizing chemical and biochemical sensors.1 The porous structure formed by the electrochemical anodic process is one of the more promising building-block candidates of the aforementioned devices. The porous alumina made from aluminum films has particular promise 2,3 because of its unique nanohole array structures, which are formed in a self-organized manner, and has been used as a template for various devices. The direct formation of porous structures has also been reported on semiconductor materials such as Si, [4][5][6]7,8 GaP,9,10 InP, 11-13 GaN, 14 and CdSe. 8 The structural properties and their tunability have been intensely investigated on III-V materials in an effort to improve electrical and optical properties.We recently succeeded in anodically forming arrays of straight nanopores on n-InP͑001͒ substrates. [15][16][17] The nanopores were laterally separated by InP nanowalls several tens of nanometers thick and formed in a straight vertical direction greater than several tens of micrometers. We previously reported that pore diameter and wall thickness can be controlled by adjusting the electrochemical anodic and cathodic conditions. 17 However, a disordered irregular layer usually forms during the initial stage of pore formation and partly remains on top of the ordered porous layer. Because this irregular layer has a thickness in the range from a few hundred nanometers to several micrometers, it degrades electrical and optical properties. Thus, complete removal of the irregular top layer has been one of the key issues in wide application of porous nanostructures for semiconductors.We report here on a photoelectrochemical ͑PEC͒ process developed to completely remove the irregular top layer from the InP porous surfaces. The PEC process can be repeated continuously after porous structures are anodically formed in the same electrolyte. Our present approach is much simpler and more controllable than other methods such as dry etching and conventional chemical etching.Our PEC process is schematically shown in Fig. 1a. The template porous structures were first formed by an anodic reaction in the dark, 16 and then the porous surface was photoelectrochemically etched in the same electrolyte...

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Electrochemical Formation of Uniform and Straight Nano-Pore Arrays on (001) InP Surfaces and Their Photoluminescence Characterizations

Cited by 63 publications

References 11 publications

Electrochemical Formation of Size-Controlled InP Nanostructures Using Anodic and Cathodic Reactions

Electrochemical Formation of Size-Controlled InP Nanostructures Using Anodic and Cathodic Reactions

Electrochemical processes for formation, processing and gate control of III–V semiconductor nanostructures

Photoelectrochemical Etching and Removal of the Irregular Top Layer Formed on InP Porous Nanostructures

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