Silicon Optoelectronic Devices Research Articles

Investigations on Optical Absorption and the Pyro-phototronic Effect with Selectively Patterned Black Silicon for Advanced Photodetection.

A novel property existing in the stain-etching technique that eliminates the need for expensive etchant masks in the texturization process of silicon wafers was identified. Through the combination of grayscale lithography and stain-etching methodologies, selective patterning of silicon with AR-P 3510 T, a positive-photoresist mask, was carried out. The etch area ratio was varied in nine different patterns of various feature sizes ranging from 400 to 1500 μm. The optical characteristics of the patterned substrates were determined from diffuse reflectance spectroscopy analysis, and the results were supported with finite-difference time-domain simulations. Complimenting the improvement in optical properties, the electrical losses in microwell-patterned photodetector devices have been reduced with an electro-optic optimum value of the surface enhancement factor, γ. The photodetecting efficiency of a selectively patterned microwell photodetector device exceeded the planar and black silicon photodetector devices with a considerable improvement in the pyro-phototronic effect. This work suggests an alternative for black silicon optoelectronic devices providing a new route to fabricate selectively patterned substrates with an achieved detectivity 16- and 20-fold higher than black and planar silicon photodetector devices, respectively.

Phenyl-Terminated Coupling Interface Enabled Highly Efficient and Stable Multiwavelength Perovskite Single Crystal/Silicon Integrated Photodetector.

The use of amino-terminated siloxanes as coupling interface for perovskite single crystals (PSCs)/silicon integrated devices has been demonstrated to be an effective method toward CMOS compatible optoelectronics; however, it suffers from the coupling stability against the hydrophilicity of the exposed terminal amino groups. In this work, a phenyl-terminated interfacial molecule, anilino-methyl-triethoxysilane (AMTES), is proposed to achieve the effectively galvanic coupling between PSCs and silicon, which can not only improve the device environmental reliability but also lower the surface energy of the silicon substrate so as to facilitate the epitaxial growth of PSCs. Benefiting from the interfacial coupling of AMTES, the obtained MAPbI3 SC/silicon integrated device possesses highly efficient multiwavelength photodetection properties across the X-ray and NIR range, which exhibits a specific detectivity D* of 3.84 × 1013 cm Hz1/2 W-1 in the visible-NIR region and an X-ray sensitivity of 1.18 × 104 μC Gyair-1 cm-2 with the lowest detection limit of 49.6 nGyair s-1. The ultra wide -3 dB bandwidth of 67,300 Hz and the linear dynamic range (LDR) of 112 dB also prove its impressive dynamic response capabilities. Moreover, the AMTES modified integrated device almost maintains 96% of the initial photodetection performance even after keeping in the atmosphere environment for 28 days. This work opens a new avenue for interfacial engineering toward the development of on-chip PSC integrated silicon optoelectronic devices.

Photodetector Based on Twisted Bilayer Graphene/Silicon Hybrid Slot Waveguide with High Responsivity and Large Bandwidth

Graphene/silicon hybrid photodetector operating at communication wavelength has attracted enormous attention recently due to its potential to realize bandwidth larger than 100 GHz. However, the responsivity is intrinsically limited by the low absorption from the atomic-thick graphene monolayer, which imposes significant obstacles towards its practical application. Although plasmonic structures has been widely applied to enhance the responsivity, it may induce the metallic absorption thus limit the responsivity lower than 0.6 A/W. Twisted bilayer graphene (TBG) has been reported to hold the ability to dramatically enhance the optical absorption due to the unique twist-angle-dependent van Hove singularities. In this article, we present a design of a silicon/TBG hybrid photodetector with a responsivity higher than 1 A/W and bandwidth exceeding 100 GHz. The enhanced responsivity is achieved by tuning the twisted angle of TBG to increase the absorption within the 1550 nm as well as utilizing the silicon slot waveguide to boost the mode overlap with TBG. The fabrication process of proposed design is also discussed demonstrating the advantages of low fabrication complexity. The proposed silicon/TBG photodetector could not only exhibit superior performance compared to previously reported silicon/monolayer graphene photodetector, but also pave the way for the practical application of graphene-based silicon optoelectronic devices.

Surface silicon nanostructure for enhancement of blue light absorption

To enhance blue light absorption, a nanohole-array was designed and fabricated on the surface of silicon. The absorptivity of the silicon/nanohole-array composite structure was simulated with the finite-difference time-domain method. The result showed that, when the air filling factor f = 0.45, the period P = 400 nm, and the hole depth d = 0.5 μm, the absorptivity of the silicon was greater than 0.85 in the blue band and the average light absorption gain was about 0.61. A nanohole-array was fabricated with these structural parameters. The experimental results showed that the blue absorptivity of the silicon was greater than 0.91 and the average light absorption gain was about 0.63. For incident light at an angle of 60°, the absorptivity was greater than 0.73 in the blue band. The research demonstrated that the blue light could be absorbed at the deeper position of Si through the nanohole-array. This research may serve as a reference for the design and fabrication of silicon optoelectronic devices with high blue light quantum efficiency.

Resistive Switching Effect of the Structure Based on Silicon Nitride

The electrophysical properties and the resistive switching effect in ITO/SiNx/Si memristor structures have been investigated. A silicon nitride film ~200 nm thick with a Si/N ratio varying with depth has been deposited on a silicon substrate by chemical vapor deposition. The current–voltage characteristics of ITO/SiNx/Si-p structures have shown that the conduction mechanism in a high-resistivity state depends on the properties of the nitride film and is described in terms of the Pool–Frenkel model, which takes into consideration electron hops between neighboring traps. When the polarity of the voltage applied to the structure changes sign, conducting channels in the nitride film break down and the structure switches over to a high-resistivity state. The photoswitching effect has been discovered in the ITO/SiNx/Si structure, which opens up a new frontier for using memristors in silicon optoelectronic devices.

STUDY ON BAND STRUCTURE OF NANOPOROUS SILICON THIN FILM

We investigate the energy band structure of nanoporous silicon thin film using first principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA). The calculation results show that the band gaps of nanoporous silicon increase with increasing porosity, increase with decreasing the thickness of matrix layer, and almost independent of the thickness of pore layer. Moreover, the band structure of nanoporous silicon can be transformed from indirect to direct gap on thin films of (111) and (110) faces. It will be the guidance and reference for the fabrication of porous silicon optoelectronic devices.

Potassium ions in SiO2: electrets for silicon surface passivation

This manuscript reports an experimental and theoretical study of the transport of potassium ions in thin silicon dioxide films. While alkali contamination was largely researched in the context of MOSFET instability, recent reports indicate that potassium ions can be embedded into oxide films to produce dielectric materials with permanent electric charge, also known as electrets. These electrets are integral to a number of applications, including the passivation of silicon surfaces for optoelectronic devices. In this work, electric field assisted migration of ions is used to rapidly drive K+ into SiO2 and produce effective passivation of silicon surfaces. Charge concentrations of up to ~5 × 1012 e cm−2 have been achieved. This charge was seen to be stable for over 1500 d, with decay time constants as high as 17 000 d, producing an effectively passivated oxide–silicon interface with SRV < 7 cm s−1, in 1 cm n-type material. This level of charge stability and passivation effectiveness has not been previously reported. Overall, this is a new and promising methodology to enhance surface passivation for the industrial manufacture of silicon optoelectronic devices.

Invited: Heterogeneously Integrated III-V on Silicon Lasers

Silicon photonics has generated an outstanding interest for optical telecommunications and inter/intra-chip interconnects in microelectronic systems. This platform can address a wide range of applications from very short distance data communication to long haul optical transmission.Recent research has focused on the realization of silicon optoelectronic integrated devices using large scale, low-cost, and highly accurate CMOS technology. While silicon is now considered as the material of choice for passive optical components due to its low-loss beyond 1.1 µm and high-index-contrast with its native oxide, it is however a very poor light-emitting material. Today, practical Si-based light sources are still missing, despite the demonstration of an electrically pumped germanium laser.Silicon-based compounds are commonly used in commercial optical waveguide devices for applications such as passive optical interconnects and biomedical sensors. However, the integration of lasers together with Si integrated photonics-electronic circuits has proved to be much more challenging. The complexity lies in the fact that silicon is a poor light-emitting material due to its indirect energy bandgap. In addition, the direct growth of standard III-V materials on Si substrates is still a major obstacle because of the mismatch in lattice constants and in thermal expansion coefficients. Although light emission from silicon is not straightforward, the development of an efficient electrically pumped laser is essential to make silicon the material of choice for monolithic optoelectronic integration.A different way consists in coupling laser beams emerging from III-V heterostructures to silicon waveguides. This so-called hybrid integration can be done using different techniques like flip-chip bonding [1] or self-assembly [2]. Both approaches present the disadvantage of requiring submicron precision alignment to enable efficient coupling between lasers and silicon waveguides. Even if the cost of a silicon photonic circuit is generally low, aligning precisely a laser chip to a planar photonic circuit is quite expensive, time consuming and unsuitable for high-volume fabrication.A particularly promising approach instead is based on molecular bonding of III-V materials on top of a patterned Si-on-Insulator (SOI) substrate. This can be performed at the die or wafer level, depending on the application needs. Then, hybrid Si/III-V lasers are realized following a collective fabrication procedure, enabling complex photonic integrated systems onto the silicon platform [3]. Using this technology, Fabry–Pérot, racetrack, distributed feedback and Bragg reflectors lasers were demonstrated [4-5].In this communication, we describe the hybrid platform and we present the recent advances on III-V/Si lasers and transmitters. References K. Kato et al., IEEE J. Sel. Tops. Quantum Electron, 6, 4-13 (2000).J. Sasaki et al., IEEE Transactions on Advanced Packaging, 24, 569-575 (2001).J.M. Fedeli et al., Advances in Optical Technologies, 2008, 412518 (2008).B. Ben Bakir et al., Opt. Exp., vol. 19, no. 11, pp. 10317–10325 (2011).A. Descos et al. Eur. Conf. Opt. Commun., Th.1.B.2, pp. 687-689, London, U.K. (2013).

실리콘 애벌런치 LED의 설계요소에 대한 분석

반도체 소자의 축소로 인한 처리속도의 향상이 더욱 어려워지고 있다. 따라서 반도체 산업의 새로운 도약을 위해서 실리콘을 이용한 광전소자의 출현(Silicon photonics)이 더욱 절실해지고 있다. 제조의 간단성, 반복성, 안정성, 고속성, 일반실리콘 반도체 공정과의 병존성 등의 특성으로 인해 애벌런치 항복에 의한 발광 소자는 실리콘 발광소자의 구현에 유력한 후보 중의 하나이다. 애벌런치 발광현상에 대해 전기적, 광학적 측정을 하고, 간단한 모델링과 시뮬레이션을 통하여 발광부위의 형태, <TEX>$n^{+}-p$</TEX> 접합의 깊이, 불순물의 농도, 에피층의 높이 등의 설계요소가 발광특성에 미치는 영향을 분석하였다. 시뮬레이션의 결과와 실제의 계측 결과를 비교하여, 차이점을 야기하는 이유, 애벌런치 항복의 발광현상을 설명하였고, 개선방안을 제시하였다. It is becoming more difficult to improve the device operating speed by shrinking the size of semiconductor devices. Therefore, for a new leap forward in the semiconductor industry, the advent of silicon opto-electronic devices, i.e., silicon photonics is more desperate. Silicon Avalanche LED is one of the prospective candidates to realize the practical silicon opto-electronic devices due to its simplicity of fabrication, repeatability, stability, high speed operation, and compatibility with silicon IC processing. We conducted the measurement of the electrical characteristics and the observation of the light-emitting phenomena using optical microscopy. We analyzed the influence of the design elements such as the shape of the light-emitting area and the depth of the <TEX>$n^{+}-p^{+}$</TEX> junction with simple device modeling and simulation. We compared the results of simulation and the measurement and explained the discrepancy between the results of the simulation and the measurement, and the suggestions for the improvement were given.

Electronic eyeballs

The ability to fabricate silicon optoelectronic devices on a curved surface will lead to imaging systems with exceptional characteristics. This innovative technology will find diverse applications.

Enhancing the Near-Infrared Spectral Response of Silicon Optoelectronic Devices via Up-Conversion

A silicon-based optoelectronic device that exhibits an enhanced response to subbandgap light is described. The device structure consists of a bifacial silicon solar cell with an up- converting (UC) layer attached to the rear. Erbium-doped sodium yttrium fluoride (NaY0.8F4 : Er0.2 3+) phosphors are the optically active centers responsible for the UC luminescence. The unoptimized device is demonstrated to respond effectively to wavelengths (lambda) in the range of 1480-1580 nm with an external quantum efficiency (EQE) of 3.4% occurring at 1523 nm at an illumination intensity of 2.4 W/cm2 (EQE = 1.4 times 10-2 cm2/W). An analysis of the optical losses reveals that the luminescence quantum efficiency (LQE) of the device is 16.7% at 2.4 W/cm2 of 1523-nm excitation (LQE = 7.0 times 10-2 cm2/W), while further potential device improvements indicate that an EQE of 14.0% (5.8 times 10-2 cm2/W) could be realistically achieved.

Recent developments in silicon optoelectronic devices

Due to the rapid growth of the internet and multi-media communication networks, there are urgent needs and tremendous commercial values in the development of optoelectronics integrated circuits (OEICs). This work reviews the recent developments and the prospect of silicon-based integrated optoelectronic circuits (Si-OEICs). The technological aspects of porous silicon and oxynitride devices for integrated optoelectronic applications are discussed. Some optoelectronic devices being realized with these technologies are described. Recent achievements indicate that the present constraints for using Si-based materials in optoelectronics are mainly technological rather than physical. Once these technological difficulties are resolved, the realization and applications of Si-OEICs will grow rapidly.

Simulation of hydrogenated amorphous and microcrystalline silicon optoelectronic devices

This paper is concerned with the modelling and simulation of amorphous and microcrystalline silicon optoelectronic devices. The physical model and its mathematical formulation are extensively described. Its numerical reduction is also discussed together with the presentation of a computer program dedicated to the simulation of the electrical behaviour of such devices. This computer program, called ASCA (Amorphous Silicon Solar Cells Analysis), is capable of simulating, on one- and two-dimensional domains, the internal electrical behaviour of multi-layer structures, homojunctions and heterojunctions under simple or complex spectra illumination and externally applied biases. The applications of the simulator presented in this work are the analysis of μc/a-Si:H p-i-n photovoltaic cell in thermal equilibrium and illuminated by monochromatic light and the AM1.5 solar spectrum, with and without polarisation. We also study the appearance within the device of lateral components of the electric field and current density vectors when the illumination is not uniform.

A silicon/iron-disilicide light-emitting diode operating at a wavelength of 1.5 μm

Although silicon has long been the material of choice for most microelectronic applications, it is a poor emitter of light (a consequence of having an ‘indirect’ bandgap), so hampering the development of integrated silicon optoelectronic devices. This problem has motivated numerous attempts to develop silicon-based structures with good light-emission characteristics1, particularly at wavelengths (∼1.5 μm) relevant to optical fibre communication. For example, silicon–germanium superlattice structures2 can result in a material with a pseudo-direct bandgap that emits at ∼1.5 μm, and doping silicon with erbium3 introduces an internal optical transition having a similar emission wavelength, although neither approach has led to practical devices. In this context, β-iron disilicide has attracted recent interest4,5,6,7,8,9,10,11,12 as an optically active, direct-bandgap material th might be compatible with existing silicon processing technology. Here we report the realization of a light-emitting device operating at 1.5 μm that incorporates β-FeSi2 into a conventional silicon bipolar junction. We argue that this result demonstrates the potential of β-FeSi2 as an important candidate for a silicon-based optoelectronic technology.

Direct measurement of the refractive index change of silicon with optically injected carriers

Silicon phase modulators are important silicon optoelectronic devices. The relationship of the refractive index change with injected carrier concentration is the basis for the operation of silicon phase modulators. No direct experimental data of this relationship have been reported. We have developed a new method for the direct measurement of this relationship using a Fabry–Perot interference and optical injection of carriers. The experimental results of the refractive index change are reported for the first time in the range of injected carrier concentration between 1013 and 1015 cm−3. It should be noted that our experiment results are about 5 to 10 times larger than those predicted by theory. The reliability of our experiments is also discussed.

Silicon optical modulators at 1.3- mu m based on free-carrier absorption

Silicon optical waveguide modulators, appropriate for operation in the 1.3-1.55 mu m wavelength region, have been fabricated and their performance characterized at the wavelength of 1.3 mu m. The modulator structures consist of p-i-n diodes integrated with silicon waveguides; device operation is based on free-carrier absorption. Modulation depths of -6.2 dB and response times less than 50 ns have been measured. Experimental results are compared with the p-i-n diode theory. It is argued that the device is suitable for integration with silicon electronics and silicon optoelectronic devices. The response times measured for the current devices may be improved by reducing the transverse dimensions of the p-i-n structure.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>