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Epitaxial III-V/Si heterojunctions for photonic devices.
KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics. (semiconductor materials)ORCID iD: 0000-0001-8630-5371
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Abstract [sv]

Monolitisk integrering av III-V material på kisel är av stort intresse för billiga och effektiva elektroniska-fotoniska komponenter och tandemsolceller på kisel. Detta är en stor utmaning på grund av defektbildning i de heteroepitaxiellt odlade materialen som orsakas av skillnaden i gitterkonstant, skillnaden i termisk expansion och olika polaritet. Detta arbete åstadkommer epitaxiella lager av III-V material på kisel med hög kvalité genom epitaxiell lateral överväxt (ELOG) och korrugerad epitaxiell lateral överväxt (CELOG) utförd i hydridgasfasepitaxi (HVPE). Vi demonstrerar både elektroluminiscens från multi-kvantbrunnstrukturer (MQW) odlade på ELOG-framställda InP/Si-substrat och fotodiodbeteende från n-InP/p-Si material framställt av CELOG. Denna avhandling fokuserar även på utförlig karaktärisering av InP/Si och GaxIn1-xP/Si framställd med CELOG, bestående av röntgendiffraktion, (tidsupplöst) fotoluminiscens, Ramanspektroskopi, katodluminiscens, samt svep- och transmissionselektronmikroskopi.Ett heltäckande InP-lager har odlats på en 3” kiselskiva genom ELOG; InP/Si skivan har sedan använts som substrat till tillverkningen av en multi-kvantbrunnbaserad lysdiod med emission vid 1550 nm. Nämnvärt stark katodluminiscens observerades över alla områden på skivan, även de där MQW – tillverkningen skedde på InP som odlats direkt över grolagret. Trots att spontan emission uppnåddes så observerades inte stimulerad emission, vilket vi främst tillskriver den ojämna ytmorfologin efter odling av MQW. Mätningar vid transparensvillkor indikerar att det uppstår förstärkning i materialet, vilket visar på potential hos tekniken för tillverkning av laser på kiselsubstrat. Problem med en viss böjning av skivan under framställningsprocessen på grund av termisk stress måste också adresseras.CELOG av InP/Si resulterade i högkristallina InP lager med en abrupt och direktövergång fri från dislokationer till kiselsubstratet trots den 8% stora skillnaden mellan materialens gitterkonstant. Frånvaron av propagerande dislokationer i materialet indikerar att de defekter som ger upphov till dessa, vilka i sin tur orsakas av skillnaden i gitterkonstant, istället begränsas till övergången – en effekt som är typisk för heterostrukturer tillverkade genom wafer-bindning. Detta indikerar att CELOG metoden agerar som en epitaxiell wafer-bindning utförd vid odlingstemperaturen. CELOG användes för att tillverka en fotodiod av en n-InP/p-Si – heteroövergång som en konceptvalidering; dioden uppmätte en maxspänning på 180 mV (VOC), en högsta strömtäthet på 1.89 mA/cm2 samt en intern och extern kvantverkningsgrad på 6% respektive 4%. Trots den låga prestandan demonstrerar detta potential hos CELOG-metoden att användas till III-V/Si integration för applikationer inom solenergi.CELOG metoden har också använts för att demonstrera en direkt GaxIn1-xP/Si – övergång som är fri från dislokationer. Som en förstudie till detta har optimering av GaInP odlad på substrat av ELOG-mönstrad GaAs utförts. Den CELOG–framställda GaInP/Si-odlingen uppvisar riktningsberoende tillväxt och anisotropi i dess sammansättning. Stapelfel uppträder i GaInP/Si-övergången, men precis som för CELOG–InP/Si så bildas inga propagerande dislokationer. Vid övergången bildades ett ~1 nm tjockt atomiskt oordnade mellanlager. GaInP–lagren är fullständigt relaxerade och ingen stress har observerats trots den 4% stora skillnaden i gitterkonstant mellan lagren och substratet. Mätningar av sammansättningen hos GaInP– lagren med direktkontakt till kiselsubstratet utförda med transmissionselektronmikroskopi och fotoluminiscens överensstämmer med varandra.Vi drar slutsatsen att det finns förbättringsmöjligheter för ELOG och CELOG–processerna för att uppnå tillräckligt hög kvalité på lagren för komponenttillverkning. Vi har demonstrerat att CELOG–metoden är en allmän teknik som kan användas för att uppnå övergångar med hög kvalité i materialsystem som är termiskt och polärt missanpassade samt har olika gitterkonstanter. Det visar på att optimerade ELOG och CELOG–processer kan möjliggöra monolitisk integrering av III-V–material på kisel för kiselfotonik och kostnadseffektiva tandemsolceller med hög verkningsgrad.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 73
Series
TRITA-SCI-FOU ; 2019:32
Keywords [en]
epitaxy, heterojunction, III-V on Si integration, solar cell
National Category
Nano Technology
Research subject
Physics
Identifiers
URN: urn:nbn:se:kth:diva-251320ISBN: 978-91-7873-230-2 (print)OAI: oai:DiVA.org:kth-251320DiVA, id: diva2:1315089
Public defence
2019-06-05, Sal B, Electrum, KTH, Kistagången 16, Kista., Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research CouncilEU, FP7, Seventh Framework ProgrammeSwedish Energy Agency
Note

QC20190514

Available from: 2019-05-14 Created: 2019-05-10 Last updated: 2019-05-14Bibliographically approved
List of papers
1. An InP/Si heterojunction photodiode fabricated by self-aligned corrugated epitaxial lateral overgrowth
Open this publication in new window or tab >>An InP/Si heterojunction photodiode fabricated by self-aligned corrugated epitaxial lateral overgrowth
2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 21, article id 213504Article in journal (Refereed) Published
Abstract [en]

An n-InP/p-Si heterojunction photodiode fabricated by corrugated epitaxial lateral overgrowth (CELOG) method is presented. N-InP/p-Si heterojunction has been achieved from a suitable pattern containing circular shaped openings in a triangular lattice on the InP seed layer on p-Si substrate and subsequent CELOG of completely coalesced n-InP. To avoid current path through the seed layer in the final photodiode, semi-insulating InP: Fe was grown with adequate thickness prior to n-InP growth in a low pressure hydride vapor phase epitaxy reactor. The n-InP/p-Si heterointerface was analyzed by scanning electron microscopy and Raman spectroscopy. Room temperature cross-sectional photoluminescence (PL) mapping illustrates the defect reduction effect in InP grown on Si by CELOG method. The InP PL intensity measured above the InP/Si heterojunction is comparable to that of InP grown on a native planar substrate indicating low interface defect density of CELOG InP despite of 8% lattice mismatch with Si. The processed n-InP/p-Si heterojunction photodiodes show diode characteristics from the current-voltage (I-V) measurements with a dark current density of 0.324 mA/cm(2) at a reverse voltage of -1V. Under the illumination of AM1.5 conditions, the InP/Si heterojunction photodiode exhibited photovoltaic effect with an open circuit voltage of 180 mV, a short circuit current density of 1.89 mA/cm(2), an external quantum efficiency of 4.3%, and an internal quantum efficiency of 6.4%. This demonstration of epitaxially grown InP/Si heterojunction photodiode will open the door for low cost and high efficiency solar cells and photonic integration of III-Vs on silicon.

Keywords
Defect density, Defects, Efficiency, Epitaxial growth, Heterojunctions, Interfaces (materials), Lattice mismatch, Open circuit voltage, Photodiodes, Photovoltaic effects, Quantum efficiency, Scanning electron microscopy, Semiconductor quantum wells, Silicon, Solar cells, Current-voltage measurements, Diode characteristics, Epitaxial lateral overgrowth, External quantum efficiency, Heterojunction photodiodes, High-efficiency solar cells, Hydride vapor phase epitaxy, Internal quantum efficiency
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-169968 (URN)10.1063/1.4921992 (DOI)000355631400048 ()2-s2.0-84930941383 (Scopus ID)
Funder
Swedish Energy AgencyVINNOVA
Note

QC 20150625

Available from: 2015-06-25 Created: 2015-06-25 Last updated: 2019-05-10Bibliographically approved
2. Epitaxial lateral overgrowth of GaxIn1-xP toward direct GaxIn1-xP/Si heterojunction
Open this publication in new window or tab >>Epitaxial lateral overgrowth of GaxIn1-xP toward direct GaxIn1-xP/Si heterojunction
Show others...
2017 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 214, no 3Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keywords
III-V semiconductors, epitaxial lateral overgrowth, GaInP, heterojunctions, silicon
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-205518 (URN)10.1002/pssa.201600631 (DOI)000397577000029 ()2-s2.0-85013663617 (Scopus ID)
Note

QC 20170509

Available from: 2017-05-09 Created: 2017-05-09 Last updated: 2019-05-10Bibliographically approved
3. Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth
Open this publication in new window or tab >>Optical and interface properties of direct InP/Si heterojunction formed by corrugated epitaxial lateral overgrowth
Show others...
2019 (English)In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 9, no 3, p. 1488-1500Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
OPTICAL SOC AMER, 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-247834 (URN)10.1364/OME.9.001488 (DOI)000460134500051 ()
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-05-10Bibliographically approved
4. Composition and interface studies of GaxIn1-xP/Si heterojunction
Open this publication in new window or tab >>Composition and interface studies of GaxIn1-xP/Si heterojunction
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Nano Technology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-251432 (URN)
Note

QC 20190617

Available from: 2019-05-14 Created: 2019-05-14 Last updated: 2019-06-17Bibliographically approved
5. Electrically pumped 1.5 μm gain material on InP/Si
Open this publication in new window or tab >>Electrically pumped 1.5 μm gain material on InP/Si
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Nano Technology
Research subject
Physics
Identifiers
urn:nbn:se:kth:diva-251434 (URN)
Note

QC 20190520

Available from: 2019-05-14 Created: 2019-05-14 Last updated: 2019-05-20Bibliographically approved

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