An Atomic Force Microscopy study of buried InAs/GaAs quantum-dot single-photon sources

Lead Research Organisation: University of Southampton
Department Name: School of Physics and Astronomy

Abstract

Conventional light sources emit a large number of photons in a wide angular range and are mainly used for illumination or imaging purposes. Technological advances have allowed the dimensions of the components of devices to be reduced to the nanometre scale, and intriguing quantum mechanical effects have come into play. We are now able to manipulate matter at the atomic level and generate single photons, the smallest constituents of light, on-demand. The ability to control light emission at its smallest level, the single photon, is technologically challenging but tremendously interesting. The next revolution in communication is expected to take place by implementing quantum devices where light-matter interaction is engineered such that information can be stored in single photons that circulate between optical cavities within a photonic network. Given their scalability and the possibility of on-chip integration, solid-state single-photon sources are expected to be the building blocks of these novel quantum architectures. If we can store information on a single photon level, we can transfer it at the speed of light with a guaranteed secure communication: any measurement by an unwanted observer will leave a trace that will be visible to the receiver, thus unveiling the steal of information. However, several challenges are still limiting the implementation of quantum information technology in everyday life: the emitted photons only preserve their properties over a very short time-scale, often requiring cryogenic-cooled emitters excited by external lasers, and networks where information can be efficiently stored and shared are still lacking.
In this project we will investigate how the presence of nanometre-scale emitters buried within a semiconductor slab affects the surface morphology and how this, in return, impacts the properties of the single photons emitted. The outcome of this work will represent a step forward in the understanding of the emission properties of quantum light sources, allowing to improve the quality and reliability of single-photon emission, essential for information technology applications, like quantum computing and cryptography.

Planned Impact

Quantum technology is currently moving beyond fundamental research laboratories and breaking into industry. Many companies are, investing in single-photon technology (e.g. Hewlett-Packard, Toshiba, IDQuantique, PicoHarp, Excelitas, Micro Photon Devices, etc.), proving the importance and timeliness of investing in this area for leveraging impact. The main beneficiaries of the proposed research are to be found in society, through the training of researchers, the investigation of faster and secure communication schemes and in industry, via the development and implementation of quantum information protocols in devices. Concerning academical impact, we will build up collaborations between overseas and national laboratories by collaborating with leading institutions in the U.S.: we will start new research projects that researchers in the U.K. will benefit from, directly (researchers in my group at the University of Southampton will interact with researchers at NIST and at The George Washington University and with our industrial partner Asylum Research) and indirectly, through the dissemination at conferences and seminars taking place in the U.K. .
 
Description In this project we have investigated how the presence of nanometre-scale emitters buried within a semiconductor slab affects the surface morphology and how this, in return, impacts the properties of the single photons emitted. The outcome of this work represents a step forward in the understanding of the emission properties of quantum light sources, allowing to improve the quality and reliability of single-photon emission, essential for information technology applications, like quantum computing and cryptography.
Exploitation Route Our findings can be used to increase the yield of fabricated quantum photonic devices embedding single photon emitters. By using the combined photoluminescence-atomic force microscopy technique that we have developed, important information on the growth of quantum emitters can be obtained. Once the emitter is located, more advanced atomic force microscopy techniques, such as multifrequency atomic force microscopy to study subsurface properties or contact mode force measurements to assess indentation levels and therefore strain properties, could also be implemented to extract structural information on the properties of buried emitters.
Sectors Education,Electronics,Other

URL https://www.nature.com/articles/s41598-017-06566-5.epdf?author_access_token=-kXDFg9K6bZMulihg1kyB9RgN0jAjWel9jnR3ZoTv0M3ZdxI0zzRl2YD1KQ7I2DzgMP_7mn7fOYy--Q2yMObpdLaQhHBCoeeUdk2XlX3IvCU0HIXsGFYjTJsgX4xeOF4UBhfweo2riipGo1fcDrjGw%3D%3D
 
Description Presentations of the results obtained to undergraduate and graduate students via talks and scientific discussions.
First Year Of Impact 2017
Sector Education,Electronics,Other
Impact Types Cultural

 
Title Combined photoluminescence imaging and atomic force microscopy (AFM) 
Description The combined photoluminescence-AFM technique that we have developed can be applied to select suitable quantum dot emitters to be integrated into photonic devices, by pre-screening not just through optical measurements, but also through the surface topography. Such an approach is expected to be beneficial for increasing the yield of fabricated photonic devices with optimal performance since it allows one to map the sample's surface quality and discard those quantum dots that appear in correspondence to morphological features that would negatively affect the optical performance of the fabricated device. In addition, we note that once a quantum dot is located, more advanced AFM techniques, such as multifrequency AFM to study subsurface properties or contact mode force measurements to assess indentation levels and therefore strain properties, could also be implemented to extract structural information on the properties of buried quantum dot sample. 
Type Of Material Technology assay or reagent 
Year Produced 2017 
Provided To Others? Yes  
Impact Improved yield of single photon devices embedding single quantum dots. 
URL https://www.nature.com/articles/s41598-017-06566-5.epdf?author_access_token=-kXDFg9K6bZMulihg1kyB9Rg...
 
Description Collaboration with National Institute of Standards and Technology (USA), The George Washington University (USA), Oxford Instruments Asylum Research (United Kingdom) 
Organisation George Washington University
Department Department of Mechanical and Aerospace Engineering
Country United States 
Sector Academic/University 
PI Contribution We are providing samples and fabricated devices and carrying out the optical and surface characterisations in Southampton and in the US.
Collaborator Contribution The National Institute of Standards and Technology in Gaithersburg hosts a state-of-the-art Nanofabrication facility that we have access to. Dedicated tools, such as a high-resolution Atomic Force Microscope (AFM), have been used for the characterisation of the devices. Through our collaborative work, samples from Kartik Srinivasan's Institute are characterised in the laboratory at the University of Southampton by the researchers working in my group. Furthermore, we can access the expertise developed in Santiago Solares' group at The George Washington University, as well as custom-made AFMs available in his laboratories. Our joint research work is developing and strengthening collaborations between the University of Southampton and U.S. research laboratories. Furthermore, we interact with Asylum Research, a company specialised in high-resolution atomic force microscopy, that is providing access to their laboratories and training to our students.
Impact This collaboration merges nanophotonics, nano fabrication and surface science. Our work is investigating how surface morphology affects the optical properties of single-photon emitters.
Start Year 2016
 
Description Collaboration with National Institute of Standards and Technology (USA), The George Washington University (USA), Oxford Instruments Asylum Research (United Kingdom) 
Organisation National Institute of Standards & Technology (NIST)
Department Center for Nanoscale Science and Technology
Country United States 
Sector Public 
PI Contribution We are providing samples and fabricated devices and carrying out the optical and surface characterisations in Southampton and in the US.
Collaborator Contribution The National Institute of Standards and Technology in Gaithersburg hosts a state-of-the-art Nanofabrication facility that we have access to. Dedicated tools, such as a high-resolution Atomic Force Microscope (AFM), have been used for the characterisation of the devices. Through our collaborative work, samples from Kartik Srinivasan's Institute are characterised in the laboratory at the University of Southampton by the researchers working in my group. Furthermore, we can access the expertise developed in Santiago Solares' group at The George Washington University, as well as custom-made AFMs available in his laboratories. Our joint research work is developing and strengthening collaborations between the University of Southampton and U.S. research laboratories. Furthermore, we interact with Asylum Research, a company specialised in high-resolution atomic force microscopy, that is providing access to their laboratories and training to our students.
Impact This collaboration merges nanophotonics, nano fabrication and surface science. Our work is investigating how surface morphology affects the optical properties of single-photon emitters.
Start Year 2016
 
Description Collaboration with National Institute of Standards and Technology (USA), The George Washington University (USA), Oxford Instruments Asylum Research (United Kingdom) 
Organisation Oxford Instruments Asylum Research
Country United States 
Sector Private 
PI Contribution We are providing samples and fabricated devices and carrying out the optical and surface characterisations in Southampton and in the US.
Collaborator Contribution The National Institute of Standards and Technology in Gaithersburg hosts a state-of-the-art Nanofabrication facility that we have access to. Dedicated tools, such as a high-resolution Atomic Force Microscope (AFM), have been used for the characterisation of the devices. Through our collaborative work, samples from Kartik Srinivasan's Institute are characterised in the laboratory at the University of Southampton by the researchers working in my group. Furthermore, we can access the expertise developed in Santiago Solares' group at The George Washington University, as well as custom-made AFMs available in his laboratories. Our joint research work is developing and strengthening collaborations between the University of Southampton and U.S. research laboratories. Furthermore, we interact with Asylum Research, a company specialised in high-resolution atomic force microscopy, that is providing access to their laboratories and training to our students.
Impact This collaboration merges nanophotonics, nano fabrication and surface science. Our work is investigating how surface morphology affects the optical properties of single-photon emitters.
Start Year 2016
 
Description Interactions with the media (press release) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Several press releases highlighting the results of our research were produced and are available online. They resulted from our interaction with journalists and websites. Examples are: New architecture could prove essential for high-performance quantum photonic circuits
https://phys.org/news/2017-11-architecture-essential-high-performance-quantum-photonic.html; Phys.org (November 2017)

Hybrid circuit combines single-photon generator and efficient waveguides on one chip
http://www.opli.net/opli_magazine/eo/2017/hybrid-circuit-combines-single-photon-generator-and-efficient-waveguides-on-one-chip-nov-news/; Opli: The Photonics Magazine (November 2017)

A Mix of Nanomaterials Leads to a New Quantum Photonic Circuit Architecture
https://spectrum.ieee.org/nanoclast/semiconductors/optoelectronics/a-mix-of-nanomaterials-leads-to-a-new-quantum-photonic-circuit-architecture;IEEE spectrum (November 2017)
Year(s) Of Engagement Activity 2017
URL https://phys.org/news/2017-11-architecture-essential-high-performance-quantum-photonic.html