Porous Silicon Multilayers and Superlattices

Agarwal, Vivechana

doi:10.1007/978-3-319-05744-6_15

Cited by 3 publications

(2 citation statements)

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“…In fact, quite complicated structures can be created with single doped layers, by changing the etch conditions during the reaction. In particular, modulation of the applied potential can create layers of different porosity, as is well established in porous silicon [53,54]. We have demonstrated this by applying the periodic potential profile shown in figure 6(a) to a sample with a 2 µm thick n-doped layer with N D ~5 × 10 18 cm −3 using the ECE set-up described in [9].…”

Section: Structuresmentioning

confidence: 77%

“…By varying the potentials and the timing of the applied potential a wide variety of morphologies could be achieved, but careful calibration of the settling time when switching is required. Using higher doped material may help to achieve sharper boundaries between layers, as has been found with porous silicon [54]. Similar methods have also been used to create porous GaN membranes, as discussed in the applications section.…”

Section: Structuresmentioning

confidence: 98%

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Porous nitride semiconductors reviewed

Griffin

Oliver

2020

J. Phys. D: Appl. Phys.

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Porous nitride semiconductors are a fast-developing area of study, which open up a wide range of new properties and applications, including strain free optical reflectors, chemical sensors and as a pathway to device lift-off. This article reviews the current progress in porous nitrides formed through electrochemical and photoelectrochemical methods. Using a simple electrochemical cell, pores are formed by injecting holes into the surface layer in order to oxidise the material into a soluble form and releasing nitrogen gas. The process is controlled principally by the electric field that drives the injection of holes and hence the applied potential and doping density are the key parameters for controlling pore morphology, along with how and whether illumination is used. We describe the mechanisms responsible for this process in detail and outline the trends for changing pore size and pore shape. For example, larger applied potential creates a larger electric field and hence larger pores. These methods have been used to produce a wide variety of different structures. We present a layered porous structure created by the modulation of the applied potential. Alternatively, layered structures can be produced by growing alternate doped and non-intentionally doped layers. Electrochemical etching can then create pores only in the doped layers, as they are conductive. This process can be performed by etching laterally through access trenches that expose the doped material or through the etching of dislocations to create nanopipes that allow subsurface porosity to form. This process requires no prior processing steps. We combine this method with patterning of surface protective layers to influence where the resulting pores grow. Based on these various fabrication processes, significant progress has been made towards applications of porous GaN across optoelectronics, sensing and for improving material quality.

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Section: Structuresmentioning

confidence: 77%

Section: Structuresmentioning

confidence: 98%

Porous nitride semiconductors reviewed

Griffin

Oliver

2020

J. Phys. D: Appl. Phys.

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Annihilating Pores in the Desired Layer of a Porous Silicon Bilayer with Different Porosities for Layer Transfer

Chiang

Lee

2019

Sci Rep

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A silicon layer that is tens of micrometers thick on a handle substrate is desired for applications involving power devices, microelectromechanical systems (MEMS), highly efficient silicon solar cells (<50 µm), etc. In general, if the initial silicon layer obtained from the layer transfer process using the etch-stop or ion-cut techniques, which may provide very accurate thickness control, is too thin, then additional epitaxial growth is required to increase the thickness of the silicon layer. However, epitaxial growth under strict predeposition conditions is a time-consuming and expensive process. On the other hand, producing porous silicon via anodization in a hydrofluoric acid solution offers an efficient way to control the dimensions of the generated pores directly on the nano- or macroscale via the current density. When sintering the porous layer via high-temperature argon annealing, the porosity of the porous layer determines whether this porous layer can serve as a device layer or a separation layer. In addition, it is clearly easier to create a transferred layer ten of micrometers thick via anodization than by ion implantation and/or epitaxial deposition.

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Influence of One-Dimensional Photonic Crystal on Raman Signal Enhancement: A Detailed Experimental Study

Krajačić,

Baran,

Tolić

et al. 2024

Appl Spectrosc

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The enhancement of Raman signals using photonic crystal structures has been the subject of numerous experimental and theoretical studies, leading to a variety of issues and inconsistencies. This paper presents a comprehensive experimental investigation into the impact of alignment between the laser excitation wavelength and the specific position of the photonic band gap on signal enhancement in Raman spectroscopy. By employing one-dimensional (1D) porous silicon photonic crystals, a systematic analysis across a large number of spectra was conducted. The study focused on examining the signal enhancement of both the Raman ∼520 cm–1 silicon band, representing the constituent material of photonic crystal, and the most prominent Raman bands of crystal violet, used as a probe molecule. The probe molecules were both infiltrated into and adsorbed on top of the photonic crystal structure. The obtained experimental results for the contribution of 1D photonic crystals to Raman signal enhancement are much smaller compared to most predictions. The Raman signal of silicon and the signal from the probe molecule are enhanced ≤2.5 times when the laser excitation aligns with the edge of the photonic band gap, strictly defined as the position at the very bottom of the reflectance peak. The results have been discussed within the context of theoretical explanations.

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Porous Silicon Multilayers and Superlattices

Cited by 3 publications

References 50 publications

Porous nitride semiconductors reviewed

Porous nitride semiconductors reviewed

Annihilating Pores in the Desired Layer of a Porous Silicon Bilayer with Different Porosities for Layer Transfer

Influence of One-Dimensional Photonic Crystal on Raman Signal Enhancement: A Detailed Experimental Study

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