Research Profile - Department of Materials Science and Metallurgy ...

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