| 1. |
- Jaramillo-Fernandez, Juliana, et al.
(författare)
-
Thermal conductivity of epitaxially grown InP : experiment and simulation
- 2017
-
Ingår i: CrystEngComm. - : ROYAL SOC CHEMISTRY. - 1466-8033. ; 19:14, s. 1879-1887
-
Tidskriftsartikel (refereegranskat)abstract
- The integration of III-V optoelectronic devices on silicon is confronted with the challenge of heat dissipation for reliable and stable operation. A thorough understanding and characterization of thermal transport is paramount for improved designs of, for example, viable III-V light sources on silicon. In this work, the thermal conductivity of heteroepitaxial laterally overgrown InP layers on silicon is experimentally investigated using microRaman thermometry. By examining InP mesa-like structures grown from trenches defined by a SiO2 mask, we found that the thermal conductivity decreases by about one third, compared to the bulk thermal conductivity of InP, with decreasing width from 400 to 250 nm. The high thermal conductivity of InP grown from 400 nm trenches was attributed to the lower defect density as the InP micro crystal becomes thicker. In this case, the thermal transport is dominated by phonon-phonon interactions as in a low defect-density monocrystalline bulk material, whereas for thinner InP layers grown from narrower trenches, the heat transfer is dominated by phonon scattering at the extended defects and InP/SiO2 interface. In addition to the nominally undoped sample, sulfur-doped (1 x 10(18) cm(-3)) InP grown on Si was also studied. For the narrower doped InP microcrystals, the thermal conductivity decreased by a factor of two compared to the bulk value. Sources of errors in the thermal conductivity measurements are discussed. The experimental temperature rise was successfully simulated by the heat diffusion equation using the FEM.
|
|
| 2. |
- Jaramillo-Fernandez, Juliana, et al.
(författare)
-
Tuning of heat transport across thin films of polycrystalline AlN via multiscale structural defects
- 2015
-
Ingår i: ECS Transactions. - : Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; , s. 53-64
-
Konferensbidrag (refereegranskat)abstract
- The effective thermal conductivity of nanocrystalline films of AlN with inhomogeneous microstructure is investigated experimentally and theoretically. This is done by measuring the thermal conductivity of the samples with the 3-omega method and characterizing their microstructure by means of electron microscopy. The relative effect of the microstructure and the interface thermal resistance on the thermal conductivity is quantified through an analytical model. Thermal measurements showed that when the thickness of an AlN film is reduced from 1460 to 270 nm, its effective thermal conductivity decreases from 8.21 to 3.12 WYm-1?K-1, which is two orders of magnitude smaller than its bulk counterpart value. It is shown that both the size effects of the phonon mean free paths and the intrinsic thermal resistance resulting from the inhomogeneous microstructure predominate for thicker films, while the contribution of the interface thermal resistance strengthens as the film thickness is scaled down. The obtained results demonstrate that the structural inhomogeneity in polycrystalline AlN films can be efficiently used to tune their cross- plane thermal conductivity. In addition, thermal conductivity measurements of epitaxially grown InP layers on silicon using Raman spectroscopy are reported.
|
|
| 3. |
- Junesand, Carl, et al.
(författare)
-
Study of planar defect filtering in InP grown on Si by epitaxial lateral overgrowth
- 2013
-
Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 3:11, s. 1960-1973
-
Tidskriftsartikel (refereegranskat)abstract
- InP thin films have been grown on InP/Si substrate by epitaxial lateral overgrowth (ELOG). The nature, origin and filtering of extended defects in ELOG layers grown from single and double openings in SiO2 mask have been investigated. Whereas ELOG layers grown from double openings occasionally exhibit threading dislocations (TDs) at certain points of coalescence, TDs are completely absent in ELOG from single openings. Furthermore, stacking faults (SFs) observed in ELOG layers grown from both opening types originate not from coalescence, but possibly from formation during early stages of ELOG or simply propagate from the seed layer through the mask openings. A model describing their propagation is devised and applied to the existent conditions, showing that SFs can effectively be filtered under certain conditions. ELOG layers grown from identical patterns on InP substrate contained no defects, indicating that the defect-forming mechanism is in any case not inherent to ELOG itself.
|
|
| 4. |
|
|
| 5. |
- Kataria, Himanshu, et al.
(författare)
-
Carrier-transport, optical and structural properties of large area ELOG InP on Si using conventional optical lithography
- 2013
-
Ingår i: 2013 International Conference on Indium Phosphide and Related Materials (IPRM). - : IEEE conference proceedings. - 9781467361309 - 9781467361316 ; , s. 6562592-
-
Konferensbidrag (refereegranskat)abstract
- We present the carrier-transport, optical and structural properties of InP deposited on Si by Epitaxial Lateral Overgrowth (ELOG) in a Low Pressure-Hydride Vapor phase epitaxy (LP-HVPE). Hall measurements, micro photoluminescence (μ-PL) and X-ray diffraction (XRD) were used to study the above-mentioned respective properties at room temperature. It is the first time that electrical properties of ELOG InP on Si are studied by Hall measurements. Prior to ELOG, etching of patterned silicon dioxide (SiO2) mask leading to a high aspect ratio, i. e. mask thickness to opening width >2 was optimized to eliminate defect propagation even above the opening. Dense high aspect ratio structures were fabricated in SiO2 to obtain ELOG InP on Si, coalesced over large area, making it feasible to perform Hall measurements. We examine this method and study Hall mobility, strain and optical quality of large area ELOG InP on Si.
|
|
| 6. |
- Kataria, Himanshu, 1983-
(författare)
-
High Quality III-V Semiconductors/Si Heterostructures for Photonic Integration and Photovoltaic Applications
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with one of the promising strategies to monolithically integrate III-V semiconductors with silicon via epitaxial lateral overgrowth (ELOG) technology and is supported by extensive experimental results. The aimed applications are light sources on silicon for electronics-photonics integration and cost effective high efficiency multijunction solar cells.The work focusses on the growth of III-V semiconductors consisting of indium phosphide (InP) and its related alloys on silicon primarily because of the bandgaps that these offer for the aimed applications. For this purpose, we make use of the epitaxial growth technique called hydride vapour phase epitaxy and exploit its near equilibrium operation capability to achieve primarily ELOG of high quality InP as the starting material on patterned InP(seed)/silicon wafer. The InP/InGaAsP layers are grown by metal organic vapour phase epitaxy.Different pattern designs are investigated to achieve high quality InP over a large area of silicon by ELOG to realise lasers. First, nano patterns designed to take advantage of aspect ratio trapping of defects are investigated. Despite substantial defect filtering insufficient growth area is achieved. To achieve a larger area, coalescence from multiple nano openings is used. Shallowly etched InP/InGaAsP based microdisk resonators fabricated on indium phosphide on silicon achieved by this method have shown whispering gallery modes. However, no lasing action is observed partly due to the formation of new defects at the points of coalescence and partly due to leakage losses due to shallow etching. To overcome these limitations, a new design mimicking the futuristic monolithic evanescently coupled laser design supporting an efficient mode coupling and athermal operation is adopted to yield large areas of ELOG InP/Si having good carrier transport and optical properties. Microdisk resonators fabricated from the uniformly obtained InP/InGaAsP structures on the ELOG InP layers have shown very strong spontaneous luminescence close to lasing action. This is observed for the first time in InP/InGaAsP laser structures grown on ELOG InP on silicon.A newly modified ELOG approach called Corrugated ELOG is also developed. Transmission electron microscopy analyses show the formation of abrupt interface between InP and silicon. Electrical measurements have supported the linear Ohmic behaviour of the above junction. This proof of concept can be applied to even other III-V compound solar cells on silicon. This allows only thin layers of expensive III-V semiconductors and cheap silicon as separate subcells for fabricating next generation multijunction solar cells with enhanced efficiencies at low cost. A feasible device structure of such a solar cell is presented. The generic nature of this technique also makes it suitable for integration of III-V light sources with silicon and one such design is proposed.
|
|
| 7. |
- Kataria, Himanshu, et al.
(författare)
-
High quality large area ELOG InP on silicon for photonic integration using conventional optical lithography
- 2014
-
Ingår i: SMART PHOTONIC AND OPTOELECTRONIC INTEGRATED CIRCUITS XVI. - : SPIE. - 9780819499028 ; , s. 898904-
-
Konferensbidrag (refereegranskat)abstract
- A simple method of growing large areas of InP on Si through Epitaxial Lateral Overgrowth (ELOG) is presented. Isolated areas of high quality InP suitable for photonic integration are grown in deeply etched SiO2 mask fabricated using conventional optical lithography and reactive ion etching. This method is particularly attractive for monolithically integrating laser sources grown on InP with Si/SiO2 waveguide structure as the mask. The high optical quality of multi quantum well (MQW) layers grown on the ELOG layer is promisingly supportive of the feasibility of this method for mass production.
|
|
| 8. |
- Kataria, Himanshu, et al.
(författare)
-
Monolithic integration of InP based structures on silicon for optical interconnects
- 2014
-
Ingår i: 2014 ECS and SMEQ Joint International Meeting. - : The Electrochemical Society. ; , s. 523-531
-
Konferensbidrag (refereegranskat)abstract
- Monolithic integration of InP based structures on Si for optical interconnects is presented. Different strategies are demonstrated to achieve requisite InP platform on Si. In the first strategy, defect free isolated areas of epitaxially and laterally overgrown InP are obtained on Si and the InGaAsP based quantum wells directly grown on these templates have shown high material quality with uniform interfaces. In the second strategy, selective area growth is exploited to achieve InP nano pyramids on Si which can be used for the growth of quantum dot structures. In the third and the final strategy, a method is presented to achieve direct interface between InP and Si using corrugated epitaxial lateral overgrowth.
|
|
| 9. |
- Kataria, Himanshu, et al.
(författare)
-
Simple Epitaxial Lateral Overgrowth Process as a Strategy for Photonic Integration on Silicon
- 2014
-
Ingår i: IEEE Journal of Selected Topics in Quantum Electronics. - 1077-260X .- 1558-4542. ; 20:4, s. 8201407-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we propose a strategy to achieve monolithic integration of III-Vs on Si for photonic integration through a simple process. By mimicking the SiO2/Si/SiO2 waveguide necessary to couple light from the gain medium on its top, we adopt a similar to 2 mu m thick silicon dioxide mask for epitaxial lateral overgrowth (ELOG) of InP on Si. The ELOG InP layer as wells as the subsequently grown quantum wells (similar to 1. 55 mu m) have been analyzed by photoluminescence and transmission electron microscopy and found to have high optical quality and very good interface. The studies are strategically important for a monolithic platform that holds great potential in addressing the future need to have an integrated platform consisting of both III-Vs and Si on same chip.
|
|
| 10. |
- Kataria, Himanshu, et al.
(författare)
-
Towards a monolithically integrated III-V laser on silicon : Optimization of multi-quantum well growth of InP on Si
- 2013
-
Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 28:9, s. 094008-
-
Tidskriftsartikel (refereegranskat)abstract
- High-quality InGaAsP/InP multi-quantum wells (MQWs) on the isolated areas of indium phosphide on silicon necessary for realizing a monolithically integrated silicon laser is achieved. Indium phosphide layer on silicon, the pre-requisite for the growth of quantum wells is achieved via nano-epitaxial lateral overgrowth (NELOG) technique from a defective seed indium phosphide layer on silicon. This technique makes use of epitaxial lateral overgrowth (ELOG) from closely spaced (1 m) e-beam lithography-patterned nano-sized openings (∼300 nm) by low-pressure hydride vapor phase epitaxy. A silicon dioxide mask with carefully designed opening patterns and thickness with respect to the opening width is used to block the defects propagating from the indium phosphide seed layer by the so-called necking effect. Growth conditions are optimized to obtain smooth surface morphology even after coalescence of laterally grown indium phosphide from adjacent openings. Surface morphology and optical properties of the NELOG indium phosphide layer are studied using atomic force microscopy, cathodoluminescence and room temperature -photoluminescence (-PL) measurements. Metal organic vapor phase epitaxial growth of InGaAsP/InP MQWs on the NELOG indium phosphide is conducted. The mask patterns to avoid loading effect that can cause excessive well/barrier thickness and composition change with respect to the targeted values is optimized. Cross-sectional transmission electron microscope studies show that the coalesced NELOG InP on Si is defect-free. PL measurement results indicate the good material quality of the grown MQWs. Microdisk (MD) cavities are fabricated from the MQWs on ELOG layer. PL spectra reveal the existence of resonant modes arising out of these MD cavities. A mode solver using finite difference method indicates the pertinent steps that should be adopted to realize lasing.
|
|
