Integration of an opto-chemical detector based on group III-nitride nanowire heterostructures

Kleindienst, Roman; Becker, Pascal; Cimalla, V.; Grewe, Adrian; Hille, Pascal; Krüger, Matthias; Schörmann, Jörg; Schwarz, Ulrich; Teubert, J.; Eickhoff, Martin; Sinzinger, Stefan

doi:10.1364/ao.54.000839

Cited by 6 publications

(3 citation statements)

References 11 publications

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“…The combination of the innovative possibilities of microstructured or free-form optical components with the new options emerging in optical system design will bring about a number of optimised optical system solutions [63,[64][65][66][67][68]. They are of fundamental importance in the realising of novel beam-shaping and -guiding concepts for ultra-compact and powerful optical units for micro-and nanostructuring, which will be integrated into the NPMM in the framework of our research work.…”

Section: Future Workmentioning

confidence: 99%

Towards alternative 3D nanofabrication in macroscopic working volumes

Kühnel

Fröhlich

Füßl

et al. 2018

Meas. Sci. Technol.

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This paper gives an overview of the research carried out at TU Ilmenau towards the development and application of tip- and laser-based nanofabrication on flat and curved surfaces in extended macroscopic working areas. It is shown that sub-10 nm structures can be fabricated by scanning probe lithography (SPL). The use of soft stamps has revealed their suitability for nanoimprinting on curved surfaces. Laser-based methods for a maskless exposure of resist on curved surfaces utilising 405 nm laser diodes have already been tested successfully. Furthermore, the current work deals with two-photon polymerisation, which has great potential with regard to the fabrication of sub-wavelength structures. At present, the methods mentioned have all been applied only in working ranges <100 × 100 μm2 in the plane and <10 μm in height. To overcome these limitations, the nanofabrication techniques are now being integrated in the nanopositioning and measuring machines (NPMMs) developed at TU Ilmenau. They offer working volumes of up to 200 × 200 × 25 mm3 with a positioning resolution of 20 pm. To provide access to any geometry elements in the 3D space with nanometre precision, the machine concepts as well as the metrological concepts are further developed. Due to the increased demands of lowest trajectory deviations within the fabrication process, new real-time controllers for probing and fabrication systems are investigated, as well as interactions in combined force and positioning sensors. Further important research is carried out into interference lithography, to enable an exposure of non-planar substrates and to improve the lateral structure resolution at the same time. A mix-and-match combination of such methods that allows the simultaneous exposure of large substrate regions with nanofabrication methods such as SPL becomes possible on the basis of the NPMMs, and is another area of great potential with regard to the research work presented in this paper.

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Section: Future Workmentioning

confidence: 99%

Towards alternative 3D nanofabrication in macroscopic working volumes

Kühnel

Fröhlich

Füßl

et al. 2018

Meas. Sci. Technol.

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“…The unique emission characteristics of the 3D microresonators can potentially be exploited in sensors and highly integrated optical microsensors [33]. We discuss a sensor that can detect tiny changes in the environment via characteristic far-field signal.…”

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confidence: 99%

Three-dimensional limaçon: Properties and applications

2017

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We perform electromagnetic wave simulations of fully three-dimensional optical Limaçon-microcavities, one basis for their future applications in microlasers and photonic devices. The analysis of the three-dimensional modes and far-fields reveals an increase of the quality factors as compared to the two-dimensional case. The structure of the far-field in the third dimension shows pronounced maxima in the emission directionality inclined to the resonator plane which may be exploited for coupling the resonator modes to the environment. This triggers ideas for technical applications, like the suggested sensor that can detect small changes in the environment based on changes in the emission profile. [14,15] which confine light in whispering gallery modes with high quality factors Q. The first microdisk-based microlasers had the drawback of isotropic light emission because of rotational symmetry. In order to observe a directional laser emission, deformed microcavities were investigated [16][17][18]. A promising shape to combine directional emission and high quality factors is the Limaçon-shape [19]. Here, ray and wave calculations based on a two-dimensional model system agree very well with the experimentally observed far-field characteristics [20][21][22][23].In reality, however, microcavities are three-dimensional (3D) objects with finite heights. This third dimension will be especially important when the cavity sizes are further reduced and both cavity height h and radius R become comparable to the wavelength [24,25]. Here, we systematically study 3D microcavities of Limaçon-shape, see left inset of FIG. 1. Its cross section in the x-y-plane is given in polar coordinates (r, φ), cf. FIG. 1, bywith mean Radius R and deformation parameter δ. We set δ = 0.43, a value known [19] to yield a highly directional far-field emission for two-dimensional (2D) cavities with refractive index n = 3.3 embedded in vacuum (n 0 = 1) as used here. We first discuss modes and farfields of 3D Limaçon cavities of varying height to radius ratio h/R, followed by outlining a sensor application based on the 3D character of the far field and its extreme sensitivity to tiny changes in the refractive index. Using MEEP [26], a free finite-difference time-domain (FDTD) software package, 3D electromagnetic wave simulations have been performed to calculate the normalized frequencies Ω = kR = Re(ω)R/c, with ω being a complex frequency and c the speed of light, the quality factors Q = −0.5Re(ω)/Im(ω), the distributions of the electric field component E z (x, y, z) (modes) and the farfield intensity I(φ, θ). As our focus is on wavelength-scale cavities, kR ranges from 1.9 up to 10.7, with k = 2π/λ being the wave number and λ the wavelength in vacuum. We use a E z -point-dipole source to excite the modes and focus on the study of TM-polarized modes.We first discuss the analogies between the structures of modes of the 2D and 3D Limaçon cavity, respectively. An example of a 2D mode and the (x, y)-cross section of a 3D mode are shown in FIG. 2 (a) and (b)...

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“…The bulky and toxic nature of the currently available UV lamps has also sparked interest in realizing portable and robust GaN based UV-LEDs. 5 Such devices employ the UV region for purposes such as water sterilisation, 9 air purication, surface disinfection, 10 non-line-of-sight conversion and space to space communication, 11,12 counterfeit detection and detectors for particle radiation, biological, 13,14 chemical agents 15 and etc. Furthermore, in many of the above mentioned devices and applications it is imperative to detect UV light without detecting the infrared or visible light, in order to minimize the chances of erroneous detection or high background.…”

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confidence: 99%

Carrier relaxation dynamics in defect states of epitaxial GaN/AlN/Si using ultrafast transient absorption spectroscopy

et al. 2015

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The relaxation dynamics of the carriers through the defect levels in an epitaxial GaN film grown with an AlN buffer layer on Si has been performed on the femto-picosecond timescale, using ultrafast transient absorption spectroscopy (UFTS). The sample was pumped above and below the band gap and probed with a white light continuum (480-800 nm). A combination of bi and triple exponential decay functions at different probe wavelengths were used to fit the kinetic profile of the carriers in the defect continuum.Based on the UFTS measurements, a model is proposed which explains the dynamics in the shallow traps and deep level defects. Furthermore, to determine the role of the lattice in the relaxation dynamics, the experiment was conducted at a low lattice temperature of 4.2 K. The relaxation constants from the UFTS measurements confirm not only the presence of shallow and deep level defects but also the involvement of phonons in one of the relaxation processes.In the last two decades gallium nitride has inspired a plethora of research activities because of its potential application in optoelectronic and photovoltaic devices such as solar cells, 1 solar-blind photodetectors, 2,3 LEDs 4-6 and laser diodes 7,8 due to its capability to tailor the band gap through the visible spectrum by alloying with Al and In. The bulky and toxic nature of the currently available UV lamps has also sparked interest in realizing portable and robust GaN based UV-LEDs.5 Such devices employ the UV region for purposes such as water sterilisation, 9 air purication, surface disinfection, 10 non-line-of-sight conversion and space to space communication, 11,12 counterfeit detection and detectors for particle radiation, biological, 13,14 chemical agents 15 and etc. Furthermore, in many of the above mentioned devices and applications it is imperative to detect UV light without detecting the infrared or visible light, in order to minimize the chances of erroneous detection or high background.16,17 It is well known that wide band gap semiconductors like GaN and ZnO have inherent defects, 18 which can signi-cantly alter the optical properties and performance of the device.19-21 Park et al. 17 report the application of a low current blocking layer of AlGaN to minimise erroneous detection. These defect components in the emission spectrum are undesirable and limit the performance of laser devices 22 and in LEDs, these defects affect the carrier injection.23,24 Hence, a detailed analysis of the non-equilibrium carrier dynamics of GaN lms in the visible region is critical not only to understand the carrier transport and relaxation process but also for optimizing the grown structure for fabrication of energy efficient optoelectronic and photovoltaic devices. The availability of ultrafast laser systems which can produce pulses in the range of femtoseconds has enabled the investigation of carrier dynamics and transitions taking place in the femto-picosecond time scale. In the current study of carrier relaxation through UFTS, which is a non-contact method t...

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Integration of an opto-chemical detector based on group III-nitride nanowire heterostructures

Cited by 6 publications

References 11 publications

Towards alternative 3D nanofabrication in macroscopic working volumes

Towards alternative 3D nanofabrication in macroscopic working volumes

Three-dimensional limaçon: Properties and applications

Carrier relaxation dynamics in defect states of epitaxial GaN/AlN/Si using ultrafast transient absorption spectroscopy

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