| 1. |
- Chuan Chen, Max, et al.
(författare)
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Low temperature activation of B implantation of Si subcell fabrication in III-V/Si tandem solar cells
- 2019
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Ingår i: Proceedings of the 36<sup>th</sup> EU PVSEC 2019. - : WIP. - 3936338604 ; , s. 764-768
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work, we investigated the Si pre-amorphization implantation (PAI) assisted low temperatureannealing process to activate boron implantation in n-Si in a hydride vapor phase epitaxy (HVPE) reactor, which canbe used for the Si subcell fabrication in the III-V/Si tandem solar cells enabled by the corrugated epitaxial lateralovergrowth (CELOG). A uniform boron activation in Si and a low emitter sheet resistance of 77 /sq was obtained atannealing temperatures of 600-700°C. High-resolution x-ray diffraction was used to study the recrystallization ofamorphous silicon and the incorporation of boron dopants in Si. Hall measurements revealed p-type carrierconcentrations in the order of 1020 cm-3. The n-Si wafers with B implantation activated at 700°C by HVPE wereprocessed to solar cells and characterized by the standard light-current-voltage measurement under AM1.5 spectrumand external quantum efficiency measurements. The developed B implantation and low temperature activationprocesses are applied to the InP/Si seed template preparation for CELOG, on which CELOG GaInP over a Si subcellwith a direct heterojunction was demonstrated.
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| 2. |
- Ha Ryu, Jae, et al.
(författare)
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Beam stability of buried-heterostructure quantum cascade lasers employing HVPE regrowth
- 2021
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 29:2, s. 2819-2826
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of beam stability for mid-infrared (IR)-emitting quantum cascade lasers (QCLs) are important for applications that require the beam to travel through air to remote targets, such as free-space communication links. We report beam-quality measurement results of narrow-ridge, 4.6 mu m-emitting buried-heterostructure (BH) QCLs fabricated using ICP etching and HVPE regrowth. Beam-quality measurements under QCW operation exhibit M-2 < 1.2 up to 1 W for similar to 5 mu m-wide ridges. 5 mu m-wide devices display some small degree of centroid motion with increasing output power (< 0.125 mrad), which corresponds to a targeting error of similar to 1.25 cm over a distance of 100 m.
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| 3. |
- Lourdudoss, Sebastian, 1953-, et al.
(författare)
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Trends in heteroepitaxy of III-Vs on silicon for photonic and photovoltaic applications
- 2017
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Ingår i: Smart Photonic and Optoelectronic Integrated Circuits XIX 2017. - : SPIE. - 0277-786X .- 1996-756X. - 9781510606555 - 9781510606562 ; 10107
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Konferensbidrag (refereegranskat)abstract
- We present and compare the existing methods of heteroepitaxy of III-Vs on silicon and their trends. We focus on the epitaxial lateral overgrowth (ELOG) method as a means of achieving good quality III-Vs on silicon. Initially conducted primarily by near-equilibrium epitaxial methods such as liquid phase epitaxy and hydride vapour phase epitaxy, nowadays ELOG is being carried out even by non-equilibrium methods such as metal organic vapour phase epitaxy. In the ELOG method, the intermediate defective seed and the mask layers still exist between the laterally grown purer III-V layer and silicon. In a modified ELOG method called corrugated epitaxial lateral overgrowth (CELOG) method, it is possible to obtain direct interface between the III-V layer and silicon. In this presentation we exemplify some recent results obtained by these techniques. We assess the potentials of these methods along with the other existing methods for realizing truly monolithic photonic integration on silicon and III-V/Si heterojunction solar cells.
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| 4. |
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| 5. |
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| 6. |
- Omanakuttan, Giriprasanth, 1989-
(författare)
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Epitaxial III-V/Si heterojunctions for photonic devices.
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Monolithic integration of III-V materials on silicon is of great interest for efficient electronic-photonic integrated devices and multijunction solar cells on silicon. However, defect formation in the heteroepitaxial layers due to lattice mismatch, thermal mismatch, and polarity mismatch makes it a great challenge. In this work, high quality III/V epitaxial layers are realised on Si by epitaxial lateral overgrowth (ELOG) and corrugated epitaxial lateral overgrowth (CELOG) techniques using a hydride vapour phase epitaxy (HVPE) reactor. We demonstrate electroluminescence of multi quantum well structure grown on InP/Si by ELOG and photodiode behaviour of CELOG n-InP/p-Si. Extensive characterization of CELOG InP/Si and CELOG GaxIn1-xP/Si is also the main subject of this thesis. This includes X-ray diffraction, (time resolved) photoluminescence, Raman spectroscopy, cathodoluminescence and scanning and transmission electron microscopies.A wafer-scale InP layer is obtained on a 3” Si wafer via ELOG. The ELOG InP/Si is then used as a substrate to fabricate a multi quantum well LED emitting at 1530 nm. Although the MQWs were grown on InP covering ELOG InP layer and InP layer on the defective seed, rather strong luminescence is observed from the electrically injected MQW on InP/Si. We identify that unsatisfactory surface morphology after MQW growth as the main factor yielding broad emission without leading to stimulated emission. However transparency condition measurements reveal that there is gain in the material indicating the potential of this technique for fabricating lasers on silicon. We need to address also the warping of ELOG/Si due to thermal strain in the device processing.CELOG of InP/Si revealed a highly crystalline InP layer on Si with an abrupt interface free of dislocations despite an 8% lattice mismatch. That misfit dislocations are confined to the interface and do not lead to threading dislocations in the layer is characteristic of the wafer bonded interface. We find the same behaviour in our CELOG InP/Si suggesting that our method acts as epitaxial wafer bonding at growth temperatures. As a proof of concept demonstration, an n-InP/p-Si heterojunction photodiode has been fabricated by CELOG technique with an open circuit voltage of 180 mV, a short circuit current density of 1.89 mA/cm2, internal quantum efficiency of 6% and external quantum efficiency of 4%. Despite low performance, this demonstrates the potential of CELOG method for III-V/Si for solar cell application.The CELOG technique is also used to demonstrate a dislocation free GaxIn1-xP/Si interface. As a pre-study GaInP growth optimization was done on ELOG patterns on GaAs substrate. CELOG GaxIn1-xP/Si exhibits orientation dependent growth and composition anisotropy. Stacking faults are observed in the CELOG GaxIn1-xP/Si interface region but no threading dislocations were observed in the interface. An atomic disorder layer of ~1nm thickness is present at the interface. The CELOG GaxIn1-xP layers are fully relaxed and no strain is observed despite a ~4% lattice mismatch.We conclude that there is room for improvement with ELOG and CELOG processes to obtain device quality III-V layers on Si. We have demonstrated that the CELOG technique is a generic technology that can be extended to realize high quality heterojunctions with mismatched material systems. Thus optimized ELOG and CELOG techniques can facilitate monolithic integration of III-V on Si for silicon photonics and high-efficiency low-cost multijunction solar cells.
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| 7. |
- Omanakuttan, Giriprasanth, et al.
(författare)
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Epitaxial lateral overgrowth of GaxIn1-xP toward direct GaxIn1-xP/Si heterojunction
- 2017
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Ingår i: Physica Status Solidi (a) applications and materials science. - : WILEY-V C H VERLAG GMBH. - 1862-6300 .- 1862-6319. ; 214:3
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Tidskriftsartikel (refereegranskat)abstract
- The growth of GaInP by hydride vapor phase epitaxy (HVPE) was studied on planar GaAs, patterned GaAs for epitaxial lateral overgrowth (ELOG), and InP/Si seed templates for corrugated epitaxial lateral overgrowth (CELOG). First results on the growth of direct GaInP/Si heterojunction by CELOG is presented. The properties of GaxIn(1-x)P layer and their dependence on the process parameters were investigated by X-ray diffraction, including reciprocal lattice mapping (XRD-RLM), scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM-EDS), photoluminescence (PL), and Raman spectroscopy. The fluctuation of Ga composition in the GaxIn(1-x)P layer was observed on planar substrate, and the strain caused by the composition variation is retained until relaxation occurs. Fully relaxed GaInP layers were obtained by ELOG and CELOG. Raman spectroscopy reveals that there is a certain amount of ordering in all of the layers except those grown at high temperatures. Orientation dependent Ga incorporation in the CELOG, but not in the ELOG GaxIn(1-x)P layer, and Si incorporation in the vicinity of direct GaxIn(1-x)P/Si heterojunction from CELOG are observed in the SEM-EDS analyses. The high optical quality of direct GaInP/Si heterojunction was observed by cross-sectional micro-PL mapping and the defect reduction effect of CELOG was revealed by high PL intensity in GaInP above Si.
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| 8. |
- Omanakuttan, Giriprasanth, et al.
(författare)
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Epitaxial lateral overgrowth of GaxIn1-xP towards coherent GaxIn1-xP/Si heterojunction by hydride vapor phase epitaxy
- 2016
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Ingår i: 2016 Compound Semiconductor Week, CSW 2016 - Includes 28th International Conference on Indium Phosphide and Related Materials, IPRM and 43rd International Symposium on Compound Semiconductors, ISCS 2016. - : IEEE. - 9781509019649
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Konferensbidrag (refereegranskat)abstract
- Epitaxial lateral overgrowth (ELOG) of GaInP on GaAs by hydride vapor phase epitaxy (HVPE) is carried out as a pre-study to obtain GaInP/Si heterointerface. We present first results on the growth of GaInP/Si by a modified ELOG technique, corrugated epitaxial lateral overgrowth (CELOG).
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| 9. |
- Omanakuttan, Giriprasanth, et al.
(författare)
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Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth
- 2019
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Ingår i: Optical Materials Express. - : OPTICAL SOC AMER. - 2159-3930 .- 2159-3930. ; 9:3, s. 1488-1500
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Tidskriftsartikel (refereegranskat)abstract
- We fabricate and study direct InP/Si heterojunction by corrugated epitaxial lateral overgrowth (CELOG). The crystalline quality and depth-dependent charge carrier dynamics of InP/Si heterojunction are assessed by characterizing the cross-section of grown layer by low-temperature cathodoluminescence, time-resolved photoluminescence and transmission electron microscopy. Compared to the defective seed InP layer on Si, higher intensity band edge emission in cathodoluminescence spectra and enhanced carrier lifetime of InP are observed above the CELOG InP/Si interface despite large lattice mismatch, which are attributed to the reduced threading dislocation density realized by the CELOG method. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 10. |
- Omanakuttan, Giriprasanth, et al.
(författare)
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Surface emitting 1.5 mu m multi-quantum well LED on epitaxial lateral overgrowth InP/Si
- 2020
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Ingår i: Optical Materials Express. - : The Optical Society. - 2159-3930 .- 2159-3930. ; 10:7, s. 1714-1723
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a surface emitting 1.5 mu m multi-quantum well (MQW) light-emitting diode (LED) on a 3-inch epitaxial lateral overgrowth (ELOG) InP/Si wafer. The enhanced crystalline quality of ELOG InP/Si is revealed by various characterization techniques, which gives rise to a MQW with high photoluminescence intensity at 1.5 mu m and interference fringes arising from the vertical Fabry-Perot cavity. The LED devices exhibited strong electroluminescence intensity that increased with pump current. Moreover, transparency current measurements indicate optical gain in the 1.5 mu m MQW on InP/Si. The results are encouraging for obtaining wafer scale 1.5 mu m surface emitting laser structures on silicon with further optimization.
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