Research Profile - Department of Materials Science and Metallurgy ...
Research Profile - Department of Materials Science and Metallurgy ...
Research Profile - Department of Materials Science and Metallurgy ...
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Rachel Oliver<br />
Royal Society University <strong>Research</strong> Fellow<br />
MEng University <strong>of</strong> Oxford<br />
PhD University <strong>of</strong> Oxford<br />
+44 (0) 1223 334469<br />
rao28@cam.ac.uk<br />
www.msm.cam.ac.uk/GaN/pages/research/oliver.htm<br />
Nitrides at the Nanoscale<br />
Working in the Cambridge GaN centre, my research focuses on<br />
the characterization <strong>and</strong> exploitation <strong>of</strong> nanoscale structures in<br />
GaN-based materials. The broad aim <strong>of</strong> my work is to achieve<br />
improved performance in GaN-based optoelectronic devices <strong>and</strong><br />
to develop <strong>and</strong> implement novel device concepts.<br />
Novel microscopy techniques for nitride<br />
semiconductors<br />
To improve the performance <strong>of</strong> GaN-based devices we need to<br />
underst<strong>and</strong> their structure <strong>and</strong> electronic properties on a micro- to<br />
nano-metre scale. New techniques are being developed to meet<br />
the dem<strong>and</strong>s <strong>of</strong> this unusual semiconductor. Our work involves: (a)<br />
applications <strong>of</strong> atomic-force microscopy (AFM) to studies not only<br />
<strong>of</strong> nitride surface topography but also <strong>of</strong> the electrical properties<br />
<strong>of</strong> nitride materials at length scales as small as 10 nm; <strong>and</strong> (b)<br />
exploiting the three-dimensional atom-probe microscope (3DAP)<br />
to determine the composition <strong>of</strong> GaN alloys, particularly InGaN<br />
quantum wells, in 3D, at a sub-nanometre scale.<br />
GaN-based single photon sources<br />
Early single-photon sources emitting in the visible spectral<br />
region were based on heavy attenuation <strong>of</strong> a laser; such sources<br />
are intrinsically unreliable, <strong>and</strong> may emit multiple photons. In<br />
contrast, we aim to build a single-photon source, based on<br />
InGaN quantum dots, that is reliable <strong>and</strong> easy to operate. Such<br />
a device would find broad application in quantum cryptography<br />
<strong>and</strong> quantum computing, particularly as the emission wavelength<br />
<strong>of</strong> the InGaN dots is rather convenient in terms <strong>of</strong> available<br />
detectors. However, the high defect density <strong>and</strong> unusual electrical<br />
properties <strong>of</strong> GaN make realising the device a challenge.<br />
AF Jarjour, RA Taylor, RA Oliver, MJ Kappers, CJ Humphreys & A Tahraoui<br />
“Cavity-enhanced blue single-photon emission from a single InGaN/GaN<br />
quantum dot” Appl. Phys. Lett. 91, 052101 (2007).<br />
MJ Galtrey, RA Oliver, MJ Kappers, CJ Humphreys, DJ Stokes, PH Clifton<br />
& A Cerezo, “Three dimensional atom probe studies <strong>of</strong> an In x<br />
Ga 1-x<br />
N/GaN<br />
multiple quantum well structure: assessment <strong>of</strong> possible indium clustering”<br />
Appl. Phys. Lett. 90, 061903 (2007).<br />
RA Oliver, MJ Kappers & CJ Humphreys, “Insights into the origin <strong>of</strong><br />
threading dislocations in GaN/Al 2<br />
O 3<br />
from atomic force microscopy” Appl.<br />
Phys. Lett. 89, 011914 (2006).<br />
RA Oliver, GAD Briggs, MJ Kappers, CJ Humphreys, JH Rice, JD Smith<br />
& RA Taylor, “InGaN quantum dots grown by MOVPE employing a postgrowth<br />
nitrogen anneal” Appl. Phys. Lett. 83, 755–757 (2003).<br />
Three-dimensional render <strong>of</strong> an atomic-force micrograph <strong>of</strong><br />
hexagonal GaN isl<strong>and</strong>s grown on sapphire<br />
32 <strong>Research</strong> <strong>Pr<strong>of</strong>ile</strong>