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High-quality InP on Si and concepts for monolithic photonic integration
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

As the age of Moore’s law is drawing to a close, continuing increase in computing performance is becoming increasingly hard‐earned, while demand for bandwidth is insatiable. One way of dealing with this challenge is the integration of active photonic material with Si, allowing high‐speed optical inter‐ and intra‐chip connects on one hand, and the economies of scale of the CMOS industry in optical communications on the other. One of the most essential active photonic materials is InP, stemming from its capability in combination with its related materials to produce lasers, emitting at wavelengths of 1300 and 1550 nm, the two most important wavelengths in data‐ and telecom.

However, integrating InP with Si remains a challenging subject. Defects arise due to differences in lattice constants, differences in thermal expansion coefficients, polarity and island‐like growth behavior. Approaches to counter these problems include epitaxial lateral overgrowth (ELOG), which involves growing InP laterally from openings in a mask deposited on a defective InP/Si substrate. This approach solves some of these problems by filtering out the previously mentioned defects. However, filtering may not be complete and the ELOG and mask themselves may introduce new sources for formation of defects such as dislocations and stacking faults.

In this work, the various kinds of defects present in InP ELOG layers grown by hydride vapor phase epitaxy on Si, and the reason for their presence, as well as strategies for counteracting them, are investigated. The findings reveal that whereas dislocations appear in coalesced ELOG layers both on InP and InP/Si, albeit to varying extents, uncoalesced ELOG layers on both substrate types are completely free of threading dislocations. Thus, coalescence is a critical aspect in the formation of dislocations. It is shown that a rough surface of the InP/Si substrate is detrimental to defect‐free coalescence. Chemical‐mechanical polishing of this surface improves the coalescence in subsequent ELOG leading to fewer defects.

Furthermore, ELOG on InP substrate is consistently free of stacking faults. This is not the case for ELOG on InP/Si, where stacking faults are to some extent propagating from the defective substrate, and are possibly also forming during ELOG. A model describing the conditions for their propagation is devised; it shows that under certain conditions, a mask height to opening width aspect ratio of 3.9 should result in their complete blocking. As to the potential formation of new stacking faults, the formation mechanism is not entirely clear, but neither coalescence nor random deposition errors on low energy facets are the main reasons for their formation. It is hypothesized that the stacking faults can be removed by thermal annealing of the seed and ELOG layers.

Furthermore, concepts for integrating an active photonic device with passive Si components are elucidated by combining Si/SiO2 waveguides used as the mask in ELOG and multi‐quantum well (MQW) lasers grown on ELOG InP. Such a device is found to have favorable thermal dissipation, which is an added advantage in an integrated photonic CMOS device.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 85 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2013:05
National Category
Nano Technology
Identifiers
URN: urn:nbn:se:kth:diva-127837OAI: oai:DiVA.org:kth-127837DiVA: diva2:646367
Public defence
2013-09-27, Sal/Hall E, Forum, KTH-ITC, Isafjordsgatan 39, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20130909

Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2013-09-09Bibliographically approved
List of papers
1. Surface morphology of indium phosphide grown on silicon by nano-epitaxial lateral overgrowth
Open this publication in new window or tab >>Surface morphology of indium phosphide grown on silicon by nano-epitaxial lateral overgrowth
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2009 (English)In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 6, no 12, 2785-2788 p.Article in journal (Refereed) Published
Abstract [en]

InP is grown on Si by nano-epitaxial lateral overgrowth (NELOG or nano-ELOG) on patterns consisting of net-type openings under different growth conditions. Surface morphology is characterized with AFM and profilometer and optical quality assessed by Micro Photoluminescence measurements (mu-PL). Results show that growth conditions affect both morphology and optical quality, with thicker layers generally corresponding to better surface morphology. Lower growth temperature seems to improve surface morphology irrespective of thickness, and ELOG layers exhibit significantly better morphology than the planar layer.

Keyword
PHOTONICS, LASER
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-29672 (URN)10.1002/pssc.200982546 (DOI)000279548000043 ()2-s2.0-77951683616 (Scopus ID)
Conference
15th International Semiconducting and Insulating Materials Conference (SIMC-XV)
Note
QC 20110218Available from: 2011-02-18 Created: 2011-02-11 Last updated: 2017-12-11Bibliographically approved
2. InP overgrowth on SiO2 for active photonic devices on silicon
Open this publication in new window or tab >>InP overgrowth on SiO2 for active photonic devices on silicon
2010 (English)In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2010, Vol. 7606Conference paper, Published paper (Refereed)
Abstract [en]

ntegrationof III-V materials on silicon wafer for active photonic deviceshave previously been achieved by growing thick III-V layers ontop of silicon or by bonding the III-V stack layersonto a silicon wafer. Another way is the epitaxial lateralovergrowth (ELOG) of a thin III-V material from a seedlayer directly on the silicon wafer, which can be usedas a platform for the growth of active devices. Asa prestudy, we have investigated lateral overgrowth of InP byHydride Vapor Phase Epitaxy (HVPE) over SiO2 masks of differentthickness on InP substrates from openings in the mask. Openingswhich varied in direction, width and separation were made withE-beam lithography allowing a good dimension control even for nano-sizedopenings (down to 100 nm wide). This mimics overgrowth ofInP on top of SiO2/Si waveguides. By optimizing the growthconditions in terms of growth temperature and partial pressure ofthe source gases with respect to the opening direction, separationand width, we show that a thin (~200 nm) layerof InP with good morphology and crystalline quality can begrown laterally on top of SiO2. Due to the thingrown InP layer, amplification structures on top of it canbe well integrated with the underlying silicon waveguides. The proposedELOG technology provides a promising integration platform for hybrid InP/siliconactive devices.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2010
Series
Proceedings of SPIE-The International Society for Optical Engineering, ISSN 0277-786X
National Category
Nano Technology Nano Technology
Identifiers
urn:nbn:se:kth:diva-13936 (URN)10.1117/12.841181 (DOI)000285576100002 ()2-s2.0-77951686688 (Scopus ID)
Conference
SPIE Photonics West 2010 Conference on Silicon Photonics V, San Francisco, CA, JAN 24-27, 2010
Note

QC 20100705

Available from: 2010-07-05 Created: 2010-07-05 Last updated: 2016-05-02Bibliographically approved
3. Morphological evolution during epitaxial lateral overgrowth of indium phosphide on silicon
Open this publication in new window or tab >>Morphological evolution during epitaxial lateral overgrowth of indium phosphide on silicon
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2011 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 332, no 1, 27-33 p.Article in journal (Refereed) Published
Abstract [en]

Epitaxial lateral overgrowth of InP from mesh and line openings on masked InP seed layer on Si(0 0 1) wafer is investigated. Coalescence occurred more rapidly from the mesh openings than from the line openings. Lethargic coalescence in the line openings is attributed to the gradual formation of growth retarding boundary planes in the initial stages of growth. Extended growth leads to complete coalescence in both types of openings. The surface roughness of the coalesced layer is inversely proportional to its thickness. Cathodoluminescence studies on the uncoalesced islands show the emergence of facets with orientation-dependent dopant concentration, but reveal no defects, in contrast to the coalesced regions. The latter are relaxed and their dislocation density deduced from panchromatic cathodoluminescence mapping varies from 6 x 10(6) to 4 x 10(7) cm(-2) depending on the layer thickness; the reduced density at higher thickness indicates partial self annihilation of dislocations. TEM cross-section studies show that most of the threading dislocations originating in the InP seed layer/Si interface are blocked by the mask, but new dislocations are generated. Some of these dislocations are associated with bounding planar defects such as stacking faults, possibly generated during lateral growth across the mask due to unevenness of the mask surface.

Keyword
Characterization, Crystal morphology, Defects, Hydride vapor phase epitaxy, Semiconductor III-V materials
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-46176 (URN)10.1016/j.jcrysgro.2011.07.022 (DOI)000295304200006 ()2-s2.0-80052330407 (Scopus ID)
Note
QC 20111102Available from: 2011-11-02 Created: 2011-11-02 Last updated: 2017-12-08Bibliographically approved
4. III-Vs on Si for photonic applications-A monolithic approach
Open this publication in new window or tab >>III-Vs on Si for photonic applications-A monolithic approach
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2012 (English)In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 177, no 17, 1551-1557 p.Article in journal (Refereed) Published
Abstract [en]

Epitaxial lateral overgrowth (ELOG) technology is demonstrated as a viable technology to realize monolithic integration of III-Vs on silicon. As an alternative to wafer-to-wafer bonding and die-to-wafer bonding, ELOG provides an attractive platform for fabricating discrete and integrated components in high volume at low cost. A possible route for monolithic integration of III-Vs on silicon for silicon photonics is exemplified by the case of a monolithic evanescently coupled silicon laser (MECSL) by combining InP on Si/SiO2 through ELOG. Passive waveguide in MECSL also acts as the defect filtering mask in ELOG. The structural design of a monolithic evanescently coupled silicon laser (MECSL) and its thermal resistivity are established through simulations. Material studies to realize the above laser through ELOG are undertaken by studying appropriate ELOG pattern designs to achieve InP on narrow regions of silicon. We show that defect-free InP can be obtained on SiO2 as the first step which paves the way for realizing active photonic devices on Si/SiO2 waveguides, e.g. an MECSL.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Heteroepitaxy, Semiconductor laser, Monolithic integration, Epitaxial lateral overgrowth, Evanescently coupled silicon laser, Silicon photonics
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
SRA - ICT
Identifiers
urn:nbn:se:kth:diva-88854 (URN)10.1016/j.mseb.2011.12.006 (DOI)000309853000007 ()2-s2.0-84866354328 (Scopus ID)
Note

QC 20121116

Available from: 2012-02-14 Created: 2012-02-14 Last updated: 2017-12-07Bibliographically approved
5. Effect of the Surface Morphology of Seed and Mask Layers on InP Grown on Si by Epitaxial Lateral Overgrowth
Open this publication in new window or tab >>Effect of the Surface Morphology of Seed and Mask Layers on InP Grown on Si by Epitaxial Lateral Overgrowth
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2012 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 41, no 9, 2345-2349 p.Article in journal (Refereed) Published
Abstract [en]

Heteroepitaxy of InP on Si by epitaxial lateral overgrowth (ELOG) using a thin seed layer of InP as starting material is investigated, with special attention given to the effect of the surface morphology of the seed and the mask layers on the quality of the ELOG layers. Chemical mechanical polishing (CMP) has been used to improve the morphological and optical quality of InP grown by hydride vapor-phase epitaxy (HVPE) using ELOG. Two approaches have been investigated: polishing the InP seed layer on Si before depositing the SiO2 mask and polishing the SiO2 mask after its deposition on the unprocessed seed layer. For polishing the InP (seed)/Si, a two-step process with an aluminum oxide- and sodium hypochlorite-containing slurry as well as a slurry based on sodium hypochlorite mixed with citric acid was used. For SiO2 mask polishing, a slurry with colloidal silica as an abrasive was employed. In both cases, the SiO2 mask was patterned with double line openings and ELOG carried out in an HVPE reactor. Morphology and crystal quality of the resulting ELOG layers were studied with atomic force microscopy (AFM) and room-temperature panchromatic cathodoluminescence (PC-CL) in situ in a scanning electron microscope (SEM), respectively. The results show that, whereas both polishing approaches result in an ELOG InP layer with good morphology, its surface roughness is lower when the InP (seed)/Si is subjected to CMP prior to deposition of the SiO2 mask, than when only the SiO2 mask is polished. This approach also leads to a decrease in the number of defects generated during coalescence of the ELOG layers.

Keyword
Heteroepitaxy, InP, hydride vapor-phase epitaxy (HVPE), epitaxial lateral overgrowth (ELOG), chemical mechanical polishing (CMP), morphology, dislocations
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-102905 (URN)10.1007/s11664-012-2164-9 (DOI)000307289400008 ()2-s2.0-84865210241 (Scopus ID)
Funder
Swedish Research Council, VR 621-2007-4661Vinnova, 2009-00548
Note

QC 20120928

Available from: 2012-09-28 Created: 2012-09-28 Last updated: 2017-12-07Bibliographically approved
6. Towards a monolithically integrated III-V laser on silicon: Optimization of multi-quantum well growth of InP on Si
Open this publication in new window or tab >>Towards a monolithically integrated III-V laser on silicon: Optimization of multi-quantum well growth of InP on Si
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2013 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 28, no 9, 094008- p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Composition changes, Epitaxial lateral overgrowth, Hydride vapor phase epitaxy, Ingaasp/inp multi-quantum wells, Lateral overgrowth, Metal organic vapor phase epitaxial growth, Monolithically integrated, Multiquantum wells
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-127836 (URN)10.1088/0268-1242/28/9/094008 (DOI)000323418400009 ()2-s2.0-84883163523 (Scopus ID)
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research VINNOVA
Note

QC 20150624

Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2017-12-06Bibliographically approved
7. Defect reduction in heteroepitaxial InP on Si by epitaxial lateral overgrowth
Open this publication in new window or tab >>Defect reduction in heteroepitaxial InP on Si by epitaxial lateral overgrowth
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2014 (English)In: Materials Express, ISSN 2158-5849, Vol. 4, no 1, 41-53 p.Article in journal (Refereed) Published
Abstract [en]

Epitaxial lateral overgrowth of InP has been grown by hydride vapor phase epitaxy on Si substrates with a thin seed layer of InP masked with SiO2. Openings in the form of multiple parallel lines as well as mesh patterns from which growth occurred were etched in the SiO2 mask and the effect of different growth conditions in terms of V/III ratio and growth temperature on defects such as threading dislocations and stacking faults in the grown layers was investigated. The samples were characterized by cathodoluminescence and by transmission electron microscopy. The results show that the cause for threading dislocations present in the overgrown layers is the formation of new dislocations, attributed to coalescence of merging growth fronts, possibly accompanied by the propagation of pre-existing dislocations through the mask openings. Stacking faults were also pre-existing in the seed layer and propagated to some extent, but the most important reason for stacking faults in the overgrown layers was concluded to be formation of new faults early during growth. The formation mechanism could not be unambiguously determined, but of several mechanisms considered, incorrect deposition due to distorted bonds along overgrowth island edges was found to be in best agreement with observations.

Keyword
Heteroepitaxy, InP on Si, Defect Characterization, Optical Properties, Lateral Overgrowth
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-127847 (URN)10.1166/mex.2014.1140 (DOI)000329798000005 ()2-s2.0-84892704735 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilVinnova
Note

QC 20140212. Updated from submitted to published.

Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2014-03-14Bibliographically approved
8. Study of planar defect filtering in InP gwoun on Si by epitaxial lateral overgrowth
Open this publication in new window or tab >>Study of planar defect filtering in InP gwoun on Si by epitaxial lateral overgrowth
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(English)Manuscript (preprint) (Other academic)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-127872 (URN)
Note

QS 2013

Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2013-09-09Bibliographically approved

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