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Morphological evolution during epitaxial lateral overgrowth of indium phosphide on silicon
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
KTH, School of Information and Communication Technology (ICT), Material Physics, Semiconductor Materials, HMA.
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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.

Place, publisher, year, edition, pages
2011. Vol. 332, no 1, 27-33 p.
Keyword [en]
Characterization, Crystal morphology, Defects, Hydride vapor phase epitaxy, Semiconductor III-V materials
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-46176DOI: 10.1016/j.jcrysgro.2011.07.022ISI: 000295304200006Scopus ID: 2-s2.0-80052330407OAI: oai:DiVA.org:kth-46176DiVA: diva2:453517
Note
QC 20111102Available from: 2011-11-02 Created: 2011-11-02 Last updated: 2017-12-08Bibliographically 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. New Methods in the growth of InP on Si and Regrowth of Semi-insulating InP for Photonic Devices
Open this publication in new window or tab >>New Methods in the growth of InP on Si and Regrowth of Semi-insulating InP for Photonic Devices
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses new methods in the growth of indium phosphide on silicon for enabling silicon photonics and nano photonics as well as efficient and cost-effective solar cells. It also addresses the renewal of regrowth of semi-insulating indium phosphide for realizing buried heterostructure quantum cascade lasers with high power and wall plug efficiency for sensing applications.

As regards indium phosphide on silicon, both crystalline and polycrystalline growth methods are investigated. The crystalline growth methods are: (i) epitaxial lateral overgrowth to realize large area InP on Si, for silicon photonics (ii) a modified epitaxial lateral overgrowth method, called corrugated epitaxial lateral overgrowth, to obtain indium phosphide/silicon heterointerface for efficient and cost effective solar cells and (iii) selective growth of nanopyramidal frusta on silicon for nanophotonics. The polycrystalline growth method on silicon for low cost solar cell fabrication has been realized via (i) phosphidisation of indium oxide coating synthesized from solution chemistry and (ii) phosphidisation cum growth on indium metal on silicon. All our studies involve growth, growth analysis and characterization of all the above crystalline and polycrystalline layers and structures.

After taking into account the identified defect filtering mechanisms, we have implemented means of obtaining good optical quality crystalline layers and structures in our epitaxial growth methods. We have also identified feasible causes for the persistence of certain defects such as stacking faults. The novel methods of realizing indium phosphide/silicon heterointerface and nanopyramidal frusta of indium phosphide on silicon are particularly attractive for several applications other than the ones mentioned here.

Both the polycrystalline indium phosphide growth methods result in good optical quality material on silicon. The indium assisted phosphidisation cum growth method normally results in larger grain size indium phosphide than the one involving phosphidisation of indium oxide. These two methods are generic and can be optimized for low cost solar cells of InP on any flexible substrate.

The method of regrowth of semi-insulating indium phosphide that is routinely practiced in the fabrication of buried heterostructure telecom laser has been implemented for quantum cascade lasers. The etched ridges of the latter can be 6-15 µm deep, which is more than 2-3 times as those of the former. Although this is a difficult task, through our quick and flexible regrowth method we have demonstrated buried heterostructure quantum cascade lasers with an output power up to 2. 5 W and wall plug efficiency up to 9% under continuous operation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xi, 84 p.
Series
TRITA-ICT/MAP AVH, ISSN 1653-7610 ; 2014:10
National Category
Engineering and Technology Nano Technology
Identifiers
urn:nbn:se:kth:diva-145375 (URN)978-91-7595-157-7 (ISBN)
Public defence
2014-06-12, Sal E, Forum, Isafjordsgatan 39, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20140523

Available from: 2014-05-23 Created: 2014-05-19 Last updated: 2014-12-18Bibliographically approved

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