Porous GaP Multilayers Formed by Electrochemical Etching

Tjerkstra, R.W.; Rivas, Jaime Gómez; Vanmaekelbergh, D.; Kelly, John J.

doi:10.1149/1.1466935

Cited by 58 publications

(50 citation statements)

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“…10 The electrochemical etching was done in an aqueous 0.5 M H 2 SO 4 solution. 9 From Table I, we observe that V max increases as the dopant density decreases. As for anodically etched Si, 11 the pore diameter, interpore distance, and porosity of GaP depend on the dopant density and on the applied potential.…”

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Tunable photonic strength in porous GaP

Rivas¹,

Lagendijk²,

Tjerkstra

et al. 2002

Applied Physics Letters

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The light-scattering properties of porous gallium phosphide, prepared by electrochemical etching, are investigated. We show that the photonic strength of the porous semiconductor can be tuned from weak to extremely strong. This tunability is related to the density and size of the pores, which are controlled by the dopant density of the GaP crystals, and the etching potential. Moreover, electrochemical etching does not introduce any significant optical absorption, which makes porous GaP suitable for many photonic applications. © 2002 American Institute of Physics. ͓DOI: 10.1063/1.1485316͔Photonic materials interact strongly with light as a result of a variation of the refractive index n on length scales of the order of the optical wavelength . The field of photonic materials has undergone a spectacular growth 1 due to the wide range of applications that they have: efficient light-emitting diodes, low-threshold lasers, microcavities, waveguides, and fast optical switches. In addition, photonic systems exhibit fascinating fundamental phenomena, such as inhibition of spontaneous emission and light localization.Pore formation by means of electrochemical etching has emerged as a very promising technique for tailoring the photonic properties of semiconductors. Most electrochemical studies have focused on silicon ͑Si͒ ͑Ref. 2͒ rather than on GaP. Si is transparent only for infrared radiation Ͼ1.1 m. In contrast, gallium phosphide ͑GaP͒ is transparent for light in the yellow and red part of the visible spectrum Ͼ0.55 m. This absence of optical absorption, together with its very high refractive index (nϭ3.3), 3 makes GaP a fascinating material for optical applications in the important wavelength range, 0.55 mϽϽ1.1 m, a range where Si shows strong absorption. In spite of this advantage, up until now, relatively little work has been performed on porous GaP. 4 Only recently, a first study of the photonic strength of porous GaP was reported:5 strong scattering of visible light without optical absorption was measured.In this letter, we show that it is easy to tune the photonic strength of porous GaP in a wide range by controlling the density and size of the pores. This tailoring can be achieved by using n-type GaP crystals with different dopant densities and by varying the etching potential. Moreover, since no optical absorption could be detected in any of the samples, porous GaP is suitable for photonic applications in the visible spectrum: these include diffuse reflectors, Bragg reflectors, and random lasers.The photonic strength is defined in terms of the transport mean free path l , which is the average length required to randomize the direction of propagation of the light by scattering. A small value of l corresponds to efficient scattering or high photonic strength. The transport mean-free path is given bywhere is the density of scatterers and is the transport cross section. 6 In our samples the pores are the scatterers, so the density of scatterers is determined by the pore density. For a given refractive-index constras...

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“…Multilayers of low porosity GaP are easy to make. 9 Such multilayers could be used as efficient one-dimensional photonic crystals or Bragg reflectors. Besides photonic applications, porous GaP can be used for micromechanical devices and sieves for biomolecules in micro total analysis systems.…”

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confidence: 99%

Tunable photonic strength in porous GaP

Rivas¹,

Lagendijk²,

Tjerkstra

et al. 2002

Applied Physics Letters

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“…4͑a͔͒. 17,18 After initial pitting of the surface, further etching proceeds in all directions radically away from the initial surface imperfection ͓Figs. 4͑b͒ and 4͑c͔͒.…”

Section: A Scanning Electron Microscopy Observationmentioning

confidence: 99%

Structural and photoluminescence properties of porous GaP formed by electrochemical etching

Tomioka

Adachi

2005

Journal of Applied Physics

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The structural and optical properties of porous GaP have been studied by scanning electron microscopy, spectroscopic ellipsometry, and photoluminescence ͑PL͒ spectroscopy. Porous GaP layers were fabricated by anodic etching in HF : H 2 O:C 2 H 5 OH=1:1:2 electrolyte on n-type ͑100͒ and ͑111͒A substrates. The morphology of the porous GaP layer is found to depend strongly on the surface orientation. Apart from the red emission band at ϳ1.7 eV, a supra-band-gap ͑E g X ͒ emission has been clearly observed on the porous GaP ͑111͒A sample. The anodic porous layer on the ͑100͒ substrate, on the other hand, has shown only the red emission at 300 K and both red and green donor-acceptor pair emissions at low temperatures. The correlation between the PL properties and the porous morphology is discussed. An optical transition model is also proposed for the explanation of the PL emission properties of the porous GaP samples.

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“…3, 8 The current density increased initially and became constant after going through a maximum. 8 When the current reached its constant level the porous layer had a thickness of ϳ2 m. From then on the thickness of the porous layer increased at a constant rate of 0.47 and 0.62 m/ min for samples A and B, respectively.…”

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“…Porous multilayers in GaP, with alternating porosity, can be formed by etching with alternating potential. 8 In several recent articles diffusive light transport in porous GaP has been considered. Optimization of the etching process of GaP has yielded the strongest random-scattering material for visible light reported to date.…”

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Electroluminescence as internal light source for measurement of the photonic strength of random porous GaP

Driel

Vanmaekelbergh

Kelly

2004

Applied Physics Letters

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During porous etching of GaP, electroluminescence ranging from the ultraviolet to the near-infrared is generated at the interface of the porous and the nonporous layer. This is used to measure the wavelength-dependent transmission of light through porous layers in a wide thickness range. Two types of porous structures, characterized by different pore sizes, were studied. The transmission of the emitted light gives valuable information about wavelength-dependent diffusion of light through porous GaP.

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Porous GaP Multilayers Formed by Electrochemical Etching

Cited by 58 publications

References 29 publications

Tunable photonic strength in porous GaP

Tunable photonic strength in porous GaP

Structural and photoluminescence properties of porous GaP formed by electrochemical etching

Electroluminescence as internal light source for measurement of the photonic strength of random porous GaP

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