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PL spectra for dry-thin solid line and wet-etched thick solid line InP/InGaAsP nanocolumns. Inset shows PL spectra of as-grown InP/ InGaAsP layer before etching.
Source publication
Two-dimensionally arrayed nanocolumns of InGaAsP/InP were fabricated using double-exposure laser holography and reactive ion etching (RIE). The size and period of nanocolumns could be controlled accurately from 80 to 150 nm in diameter and 220 to 450 nm in period by changing the incident angle of the laser beam. RIE for a typical time of 30 min usi...
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... investigate the effect of RIE on the optical properties of nano- columns, a PL measurement was performed at room temperature. Figure 5 shows the PL spectra of the as-grown and the etched InP (t 20 nm)/InGaAsP ( 1.32 m and t 250 nm) films in which the formation of InGaAsP nanocolumns was also confirmed by SEM. While the as-grown sample shows weak luminescence at 932 nm 1.33 eV and strong luminescence at 1.32 m originating from the InP and InGaAsP layers, respectively inset of Fig. 5, the etched sample shows a strongly enhanced luminescence at 932 nm and a weak luminescence at 1.32 m. ...
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... 5 shows the PL spectra of the as-grown and the etched InP (t 20 nm)/InGaAsP ( 1.32 m and t 250 nm) films in which the formation of InGaAsP nanocolumns was also confirmed by SEM. While the as-grown sample shows weak luminescence at 932 nm 1.33 eV and strong luminescence at 1.32 m originating from the InP and InGaAsP layers, respectively inset of Fig. 5, the etched sample shows a strongly enhanced luminescence at 932 nm and a weak luminescence at 1.32 m. The weak luminescence of an as-grown sample at 932 nm can be explained by the absorption of light through the unetched InGaAsP layer, while the strong enhance- ment of the etched sample is explained by the etched InGaAsP layer, free ...
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... damage. 17 In this regard, we performed a wet chemical treatment for damage curing. After dipping in HBr/H 2 O 2 /H 2 O solution volume ratio of 8/2/100 for 3 s etch rate of 3 nm/s, both PL intensities from the InP and InGaAsP layers were increased due to removal of etch-induced dam- age, similar to the results of Baba and Matsuzaki 7 as shown in Fig. 5. This indicates the practical importance of the wet etching process for the fabrication of high quality ...
Citations
... [1][2][3]. It has been extensively used in the fabrication of nanopores in silicon [4], memory devices [5], multilevel interconnect Si devices [6], photonic crystals [7,8], three-dimensional micro-and nanostructures [9] and microelectromechanical systems [10]. The benefits of RIE have been realized in the photovoltaic (PV) industry as well, particularly in the area of surface texturing to enhance light absorption and improve the solar cell performance. ...
... Interference lithography (IL) is commonly used to produce periodic and quasi-periodic patterns with nanoscale features [1][2][3][4][5]. While the initial pattern is produced in photoresist, it can then be used with a wide variety of nanofabrication techniques to produce nanostructured devices with many applications, including photonic crystals [6][7][8][9][10][11][12], plasmonic devices [11,[13][14][15], wire grid polarizers [16,17], biomimetics [18], and microfluidics [19]. 3 Present address: NaMLab, Germany. ...
... Interference lithography (IL) is commonly used to produce periodic and quasi-periodic patterns with nanoscale features [1][2][3][4][5]. While the initial pattern is produced in photoresist, it can then be used with a wide variety of nanofabrication techniques to produce nanostructured devices with many applications, including photonic crystals [6][7][8][9][10][11][12], plasmonic devices [11,[13][14][15], wire grid polarizers [16,17], biomimetics [18], and microfluidics [19]. 3 Present address: NaMLab, Germany. ...
... For example, using positive photoresist, an area receiving a higher local dose will result in a smaller remaining photoresist feature. This is a serious issue for many photonics-based devices, including wire grid polarizers [16,17], plasmonic devices [11,15], and hole diameters in 2D photonic crystals [6,7,10,12]. ...
The non-uniform intensity profile of Gaussian-like laser beams used in interference lithography (IL) leads to a non-uniform dose and feature size distribution across the sample. Previously described methods to improve dose uniformity are reviewed. However, here we examine the behavior of the non-uniformity from the viewpoint of photoresist response rather than the IL system configuration. Samples with a fixed intra-sample dose profile were exposed with an increasing average dose. A line/space pattern with a period of 240 nm across an area of 2 × 2 cm(2) was produced using IL on identical samples using a HeCd laser operated at 325 nm and a Lloyd's mirror IL system. A binary model of photoresist response predicts that the absolute range of line widths in nanometers should be significantly reduced as the overall sample dose is increased. We have experimentally verified a reduction in the range of line widths within a given sample from 50 to 16 nm as the overall dose is increased by only 60%. This resulted in a drop in the narrowest line width from 120 to 65 nm. An etch process is demonstrated to increase the line width by generating a wider secondary chrome hard mask from the narrowly patterned primary chrome hard mask. The subsequent fabrication of a silicon nanoimprint mold is used as a demonstration of the technique.
... Numerous fabrication methods, such as photolithography, nanoimprint, and electron-beam writing [9] were used to form the submicrometer patterns on the substrate . It is noteworthy that the laser interference lithography (LIL) method is a low cost, maskless method for rapidly patterning the submicrometer array on the substrate101112. APhC was applied on the sapphire substrate to enhance the light extraction efficiency of the gallium nitride (GaN) lightemitting diode (LED) that was laid on the other side of the sapphire [13] . ...
We applied the laser interference lithography method to form a patterned sapphire substrate (PSS). A three-dimensional photonic crystal was formed by autocloning the PSS with alternate Ta2O5/SiO2 coatings. A high total integrated reflectance (TIR) band was obtained around the 410 to 470 nm wavelength range that matched the emission spectrum of the gallium nitride (GaN) light-emitting diode (LED) for application in manipulating the light extraction of the sapphire-based GaN LED. (C) 2010 Optical Society of America
... Reactive Ion Etching (RIE) is used in the fabrication of some types of speciality silicon solar cells because it provides a highly anisotropic etch profile with good etchmask selectivity, is suitable for complicated etch patterns and is free from dangerous wet chemicals [1][2][3]. It has been extensively used in fabrication of nanopores in silicon [4], memory devices [5], multilevel interconnect Si devices [6], photonic crystals [7,8] and microelectromechanical systems [9]. ...
Reactive Ion Etching (RIE) is used in the fabrication of some types of solar cells to achieve a highly directional etch. However, cells fabricated using RIE have lower than expected efficiency, possibly caused by increased carrier recombination. Characterisation of the carrier lifetime in solar cells was conducted using the quasi steady state photoconductance (QSSPC) measurement technique. Substantial effective lifetime degradation was observed for silicon samples processed by RIE. Lifetime degradation for samples where RIE etches into silicon is found to be permanent, while for samples where RIE etches only on dielectric layers of SiO2 grown on the wafer, the lifetime degradation is found to be reversible. The reversible degradation in RIE-processed samples is associated with radiation damage. By reducing the proportion of a wafer exposed to RIE, the degradation of the effective lifetime of RIE-etched silicon samples can be minimised, andtheperformance of siliconsolar cellscanbe improvedsignificantly. Copyright#2010JohnWiley &Sons, Ltd.
A method to record the holographic gratings for achieving variable output intensity in different exposure zones is proposed. The desired periodic fringes are obtained according to the analytical formula based on interference. Numerical results show that the method can fabricate the gratings with variable modulated intensity successfully.
Two-dimensionally arrayed nanocolumn lattices were fabricated by using double-exposure laser holographic method. The hexagonal lattice was formed by rotating the sample with 60 degree while the square lattice by 90 degree before the second laser-exposure. The reactive ion etching for a typical time of 30 min using CH/H plasma enhanced the aspect-ratio by more than 1.5 with a slight increase of the bottom width of columns. The etch-damage was observed by photoluminescence (PL) spectroscopy which was removed by the wet chemical etching using HBr// solution, leading into the enhanced PL intensities of the PCs. ? n?? ??? ??? ? ? ??? ??? 惺?? ? ? ??? ??? 棺?? ? ? ヱ?? ??? 탺?? ? 저 ??? ??? ??? ? ? ??? ??? u?? ? 저 惱?? ??? 주?? ? ? 烱?? ??? ??? ? ? 胱?? ??? ??? ? ? ? ?돀で?? ??? 傅??
Two-dimensionally arrayed nanocolumns were fabricated by using a double-exposure laser holography method. The hexagonal lattice was formed by rotating the sample with 60° while the square lattice by 90° before the second laser exposure. The size and period of nanocolumns could be controlled accurately from 80 to 150 nm in diameter and 220 to 450 nm in period for square lattice by changing the incident angle of laser beam. The reactive ion etching (RIE) for a typical time of 30 min using CH4/H2 plasma enhanced the aspect ratio by more than 1.5 with a slight increase of the bottom width of columns. Furthermore, it was observed that a wet etching after reactive ion etching enhanced the photoluminescence intensity of nanocolumns due to the removal of sidewall damage.
We have demonstrated the improvement of the light-output power of GaN-based light-emitting diodes (LEDs) using hole-patterned indium tin oxide (ITO) p-type electrodes. Hole patterns were defined by a laser holographic lithography combined with a postlithography deposition process. It is shown that near-UV LEDs made with the patterned ITO with a hole period of 710 nm and a size of 320 nm give 23% and 67% higher light-output power (at 20 mA) than those of LEDs with unpatterned ITO and Ni/Au contacts, respectively. It is further shown that the reduction of the hole period results in an additional improvement of light-output power.
GaN-based light-emitting diode (LED) with SiO2 photonic crystals (PCs) structure made by holographic lithography on an indium-tin-oxide (ITO) film was fabricated. The PCs made on SiO2 but an ITO film both improves the light extraction efficiency of the GaN-based LED and prevents the sheet resistance increasing of the ITO film from the dry etching damage. It was found that the forward voltage at 20 mA of the GaN-based LED with SiO2 PCs on an ITO film was 1.9% higher than the GaN-based LED with a planar ITO film only. The output power of GaN-based LED with SiO2 PCs on an ITO film at 20mA was 17.1%, 26.5% and 125.3% higher than that of the GaN-based LEDs with the planar SiO2/ITO, planar ITO or Ni/Au surface layers, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
