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Towards a monolithically integrated III-V laser on silicon: Optimization of multi-quantum well growth of InP on Si
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
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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.

Place, publisher, year, edition, pages
2013. Vol. 28, no 9, 094008- p.
Keyword [en]
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: urn:nbn:se:kth:diva-127836DOI: 10.1088/0268-1242/28/9/094008ISI: 000323418400009Scopus ID: 2-s2.0-84883163523OAI: oai:DiVA.org:kth-127836DiVA: diva2:646366
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
In thesis
1. High-quality InP on Si and concepts for monolithic photonic integration
Open this publication in new window or tab >>High-quality InP on Si and concepts for monolithic photonic integration
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:nbn:se:kth:diva-127837 (URN)
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
2. High Quality III-V Semiconductors/Si Heterostructures for Photonic Integration and Photovoltaic Applications
Open this publication in new window or tab >>High Quality III-V Semiconductors/Si Heterostructures for Photonic Integration and Photovoltaic Applications
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. ix, 61 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610
National Category
Nano Technology Telecommunications Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-153946 (URN)978-91-7595-289-5 (ISBN)
Public defence
2014-10-31, SAL A, Electrum, Isafjordsgatan 22, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20141010

Available from: 2014-10-10 Created: 2014-10-10 Last updated: 2014-10-10Bibliographically approved

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