ORCID Profile
0000-0001-5960-7438
Current Organisation
University of Western Australia
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-1997
DOI: 10.1109/55.596934
Publisher: IOP Publishing
Date: 13-10-2006
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2001
DOI: 10.1109/16.906440
Publisher: Elsevier BV
Date: 02-2013
Publisher: AIP Publishing
Date: 03-2007
DOI: 10.1063/1.2435972
Abstract: The effect of isochronal thermal annealing on Ni∕n-GaN Schottky barrier diodes exposed to a total accumulated gamma-ray dose of 21 Mrad(Si) has been investigated using capacitance-voltage (C-V) and current-voltage (I-V) measurements, while capacitance deep-level transient spectroscopy (DLTS) has been employed to monitor the evolution and annihilation of radiation-induced defects during thermal annealing. Annealing temperatures up 160 °C were found to improve device I-V characteristics however, thermal annealing above 250 °C resulted in: (a) Degradation of both forward and reverse I-V characteristics, (b) reduction in free carrier concentration, and (c) a decrease in the concentration of radiation-induced defects, as evidenced by DLTS measurements. Following annealing above 350 °C, the radiation-induced defects were no longer detectable using DLTS. Analysis of the thermally induced reduction in radiation-induced defect concentration indicated that the dominant defect-annihilation process has a mean activation energy of 1.8 eV. The physical origin of radiation-induced defects, and of defects involved in their annihilation process, is discussed in the perspective of published theoretical calculations of native defect diffusion mechanisms in GaN.
Publisher: Elsevier BV
Date: 2018
Publisher: Wiley
Date: 22-05-2007
Publisher: Wiley
Date: 30-04-2018
Abstract: Density functional theory calculations are used to study the molecular and dissociative adsorption of water on the (-201) β-Ga
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 04-2011
Publisher: IEEE
Date: 21-11-2022
Publisher: IEEE
Date: 2000
Publisher: Springer Science and Business Media LLC
Date: 27-11-2008
Publisher: The Electrochemical Society
Date: 2010
DOI: 10.1149/1.3489075
Publisher: AIP Publishing
Date: 30-05-2011
DOI: 10.1063/1.3595341
Abstract: Magnetic-field dependent Hall-effect measurements and mobility spectrum analysis were employed to study anisotropic transport in N-polar GaN/Al0.3Ga0.7N heterostructures grown on vicinal sapphire substrates. The significant anisotropy in the mobility in the parallel and perpendicular directions to the miscut direction was accompanied by a slight anisotropy in charge density. A single electron species was found in the direction parallel to the steps resulting from growth on the vicinal substrates while in the perpendicular direction two distinct electrons peaks were evident at T≤150 K. The lower average mobility in the perpendicular direction is attributed to interface roughness scattering.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2001
DOI: 10.1109/16.906450
Publisher: Wiley
Date: 17-04-2023
Abstract: Direct laser writing (DLW) of mesoporous porous silicon (PS) films is shown to selectively create spatially separated nitridized and carbonized features on a single film. Nitridized or carbonized features are formed during DLW at 405 nm in an ambient of nitrogen and propane gas, respectively. The range of laser fluence required to create varying feature sizes while avoiding damage to the PS film is identified. At high enough fluence, nitridation using DLW has been shown as an effective method for laterally isolating regions on the PS films. The efficacy in preventing oxidation once passivated is investigated via energy dispersive X‐ray spectroscopy. Changes in composition and optical properties of the DL written films are investigated using spectroscopic analysis. Results show carbonized DLW regions have a much higher absorption than as‐fabricated PS, attributed to pyrolytic carbon or transpolyacetylene deposits in the pores. Nitridized regions exhibit optical loss similar to previously published thermally nitridized PS films. This work presents methods to engineer PS films for a variety of potential device applications, including the application of carbonized PS to selectively engineer thermal conductivity and electrical resistivity and of nitridized PS to micromachining and selective modification of refractive index for optical applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2003
Publisher: Wiley
Date: 28-04-2008
Publisher: IOP Publishing
Date: 21-02-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2011
Publisher: IEEE
Date: 12-2018
Publisher: IEEE
Date: 12-2018
Publisher: Elsevier BV
Date: 05-2019
Publisher: Elsevier BV
Date: 07-2000
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 04-2010
Publisher: SPIE
Date: 30-03-2004
DOI: 10.1117/12.527255
Publisher: IEEE
Date: 2002
Publisher: Elsevier BV
Date: 12-2005
Publisher: Elsevier BV
Date: 09-2009
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2015
Publisher: AIP Publishing
Date: 30-06-2004
DOI: 10.1063/1.1760840
Abstract: The transient behavior of persistent photoconductivity (PPC) in unintentionally doped GaN has been investigated for different excitation intensities and at different temperatures. The observed PPC buildup behavior can be described by a sum of two exponential functions with a long and a short time constant, which are attributed separately to the contributions of an electron trap and a hole trap, respectively. The concentrations of the electron trap and hole trap at 300 K are 1.6×1015 and 2.6×1015 cm−3, with a thermal activation energy level of 195.5 and 111.6 meV, respectively. Temperature dependence of the PPC buildup processes indicates that from 340 K down to about 240 K the rate parameters associated with the PPC buildup are dominated by the thermally activated capture mechanisms of defects. In contrast they are nearly independent of temperature below 240 K.
Publisher: Elsevier BV
Date: 03-2014
Publisher: IEEE
Date: 12-2010
Publisher: IEEE
Date: 12-2010
Publisher: Elsevier BV
Date: 02-1998
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 15-06-2023
Publisher: Wiley
Date: 11-04-2005
Publisher: Elsevier BV
Date: 02-2022
Publisher: No publisher found
Date: 2000
DOI: 10.1063/1.126962
Publisher: AIP Publishing
Date: 20-01-2004
DOI: 10.1063/1.1635977
Abstract: The optical quenching of photoconductivity in undoped n-type GaN has been investigated. It was observed that for increasing 360 nm background intensity, at constant 632 nm quenching illumination intensity, the quenching increased for intensities up to 1012 photons cm−2 s−1 and decreased thereafter. At low background illumination intensities, the transient in photoconductivity induced by the quenching illumination exhibits a sharp rise followed by a slow decay removal of the quenching illumination was also noted to induce a sharp photocurrent drop followed by a slow recovery to the photocurrent level induced by the background illumination alone. The quenching effect at constant background and quenching illumination wavelength and intensity is noted to keep nearly constant at low temperature and decrease rapidly when temperature is higher than 270 K. Furthermore, measurement of the spectral distribution of the quenching effect indicates the existence of a broadband hole trap centered around 1.5 eV above the valence band. To explain the observed experimental behavior, the conventional hole trap and recombination center model was extended to include an electron trap. This extended model was found to accurately predict the experimental results.
Publisher: The Electrochemical Society
Date: 2009
DOI: 10.1149/1.3174319
Publisher: AIP Publishing
Date: 31-05-2002
DOI: 10.1063/1.1483390
Abstract: Transient capacitance measurements of Schottky diodes fabricated on nominally undoped n-type GaN exposed to 60Co gamma irradiation indicate the introduction of two defect levels with thermal activation energies of 89±6 and 132±11 meV. While the emission characteristics of these defects manifest significant broadening, their parameters are consistent with reported electron-irradiation-induced nitrogen-vacancy related centers. Three deep-level defects present before irradiation exposure with activation energies of 265, 355, and 581 meV were found to remain unaffected for cumulative gamma-ray doses up to 21 Mrad(Si).
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 09-2021
Publisher: AIP Publishing
Date: 05-07-2010
DOI: 10.1063/1.3462323
Abstract: We have investigated the pH and ion sensitivity of AlGaN/GaN heterostructure devices these devices are sensitive to the ion concentration rather than to the pH of the solution. Sheet resistance as a function of pH for calibrated pH solutions and dilute NaOH, HCl, KOH, and NaCl showed an increase as a function of ionic concentration, regardless of whether the pH was acidic, basic, or neutral. An increase in resistance corresponds to accumulation of negative ions at the AlGaN surface, indicating device selectivity toward the negative ions. We attribute this to the formation of a double layer at the liquid/semiconductor interface.
Publisher: Elsevier BV
Date: 11-1995
Publisher: Springer Science and Business Media LLC
Date: 20-07-2007
Publisher: IOP Publishing
Date: 05-09-2006
Publisher: Elsevier BV
Date: 03-2022
Publisher: AIP Publishing
Date: 12-07-1999
DOI: 10.1063/1.124337
Abstract: Solar-blind ultraviolet photodiodes with a band-edge wavelength of 285 nm were fabricated on laterally epitaxially overgrown GaN grown by metalorganic chemical vapor deposition. Current–voltage measurements of the diodes exhibited dark current densities as low as 10 nA/cm2 at −5 V. Spectral response measurements revealed peak responsivities of up to 0.05 A/W. Response times for these diodes were measured to be as low as 4.5 ns for 90%-to-10% fall time. For comparison, diodes were fabricated using the same p–i–n structure deposited on dislocated GaN. These diodes had dark current densities many orders of magnitude higher, as well as a less sharp cutoff, and a significant slow tail under impulse excitation.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 03-2023
Publisher: AIP Publishing
Date: 14-05-2001
DOI: 10.1063/1.1372620
Abstract: The effect of the growth conditions of the top 2.5 nm thick AlGaN cap layer and wafer cool down conditions on AlGaN/GaN high electron mobility transistor performance was investigated. The AlGaN/GaN heterostructures were deposited on sapphire by metalorganic chemical vapor deposition and consisted of a 3 μm thick semi-insulating GaN layer and an 18 nm thick Al0.33Ga0.67N layer, the top 2.5 nm of which was deposited under various conditions. The power performance of the devices severely degraded for all s les where the Al content of the top 2.5 nm of AlGaN was increased and/or the ammonia flow during growth of the top layer was decreased. A modest improvement in the output power density was observed when the growth conditions of the cap layer were identical of those of the rest of the AlGaN layer, but when the wafer was cooled down in pure nitrogen.
Publisher: Institution of Engineering and Technology (IET)
Date: 2003
DOI: 10.1049/EL:20030872
Publisher: Elsevier BV
Date: 07-2011
Publisher: Elsevier BV
Date: 02-2011
Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.JCIS.2019.08.079
Abstract: The surface charge of gallium nitride (GaN) in contact with solution is controlled by pH via surface protonation and deprotonation, similar to silica. Ionic surfactants adsorb on surfaces via electrostatic and hydrophobic interactions and can be utilized to reflect the surface charge of GaN. The surface charge properties of Ga-polar GaN in solution were probed as a function of pH using atomic force microscopy (AFM). AFM soft-contact images and force curves were used to study the pH-dependent adsorption of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and anionic surfactant sodium dodecylsulfate (SDS) on GaN surfaces. To further confirm the AFM results, GaN/AlGaN/GaN heterostructure-based ion sensing devices were used to measure the surfactant adsorption over the same pH range. SDS aggregates adsorb on GaN below pH 2.75 while CTAB aggregates adsorb above pH 10. This shows that the GaN surface carries substantial net positive charge at low pH, and negative charge at high pH. There is no clear SDS or CTAB adsorption on the GaN surface between pH 3 and 9.75, which indicates the surface is weakly charged. GaN/AlGaN/GaN heterostructure-based devices confirm these results, and demonstrate the utility of these devices for measuring surfactant adsorption.
Publisher: Elsevier BV
Date: 07-2012
Publisher: Springer Science and Business Media LLC
Date: 22-08-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2021
Publisher: Elsevier BV
Date: 05-2013
Publisher: AIP Publishing
Date: 23-11-1998
DOI: 10.1063/1.122701
Abstract: Self-aligned AlGaN/GaN modulation-doped field-effect transistors (MODFETs) with high transconductances have been demonstrated on a sapphire substrate. Source and drain were selectively regrown with ∼1700 Å of n-GaN adjacent to the gate electrode. Source resistance was reduced to 0.95 Ω mm from 1.4 to 1.8 Ω mm with conventional GaN-based MODFETs. These self-aligned devices show a record high value of extrinsic transconductance ∼400 mS/mm for AlGaN/GaN MODFETs with a gate length of 1.2 μm.
Publisher: Elsevier BV
Date: 2021
Publisher: IEEE
Date: 12-2010
Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 09-2014
Publisher: IEEE
Date: 2002
Publisher: Elsevier BV
Date: 2021
Publisher: IEEE
Date: 12-2014
Publisher: Springer Science and Business Media LLC
Date: 15-11-2008
Publisher: Wiley
Date: 05-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2012
Publisher: Springer Science and Business Media LLC
Date: 24-11-2012
Abstract: Transmission diffraction gratings operating at 1,565 nm based on multilayer porous silicon films are modeled, fabricated, and tested. Features down to 2 μm have been patterned into submicron-thick mesoporous films using standard photolithographic and dry etching techniques. After patterning of the top porous film, a second anodization can be performed, allowing an under-layer of highly uniform porosity and thickness to be achieved. High transmission greater than 40% is measured, and modeling results suggest that a change in diffraction efficiency of 1 dB for a 1% change in normalized refractive index can be achieved. Preliminary measurement of solvent vapor shows a large signal change from the grating sensor in agreement with models.
Publisher: AIP Publishing
Date: 23-10-2000
DOI: 10.1063/1.1319528
Abstract: Dislocation reduction in GaN films grown on sapphire and silicon substrates was achieved by inserting thin InGaN layers grown in a selective island growth mode after partial passivation of the GaN surface with a submonolayer of silicon nitride. We show that this technique is most effective at reducing the pure edge dislocation density when it is high (i.e., & cm−2) and less when the density is in the 108–109 cm−2 range. Thus, the structural quality of typically highly dislocated GaN on silicon films could be significantly improved, visible in a reduction of the (0002) full width at half maximum (FWHM) from 1300 arcsec for ordinary GaN on silicon to 800 arcsec for GaN films with silicon nitride/InGaN interlayers. In the case of GaN layers grown on sapphire (dislocation density ∼109 cm−2), the method resulted mainly in a reduction of the FWHM of the (101̄2) and (202̄1) diffraction peaks.
Publisher: Springer Science and Business Media LLC
Date: 25-10-2008
Publisher: AIP Publishing
Date: 15-08-2012
DOI: 10.1063/1.4746740
Abstract: The zero-bias spectral response of a p-type GaN Schottky diode with an acceptor doping density of 1019 cm−3 was measured, and the electron diffusion length was calculated using the standard theoretical equation that relates this parameter to the measured photocurrent. Here it is shown that the minor but perceptible spectral variation of the diffusion length calculated can be explained by taking into account the Franz-Keldysh effect. Consideration of this effect, through the use of an equation that describes the electric field and spectral dependence of the absorption coefficient, leads to a constant diffusion length value of 14 nm. By also taking into account the inherent inaccuracy of the theoretical equation, a final value of 10 nm was estimated for the electron diffusion length.
Publisher: Elsevier BV
Date: 03-2011
Publisher: Wiley
Date: 02-12-2010
Publisher: AIP Publishing
Date: 15-04-2000
DOI: 10.1063/1.372432
Abstract: In order to characterize the electron transport properties of the two-dimensional electron gas (2DEG) in AlGaN/GaN modulation-doped field-effect transistors, channel magnetoresistance has been measured in the magnetic field range of 0–12 T, the temperature range of 25–300 K, and gate bias range of +0.5 to −2.0 V. By assuming that the 2DEG provides the dominant contribution to the total conductivity, a one-carrier fitting procedure has been applied to extract the electron mobility and carrier sheet density at each particular value of temperature and gate bias. Consequently, the electron mobility versus 2DEG sheet density has been obtained for each measurement temperature. Theoretical analysis of these results suggests that for 2DEG densities below 7×1012 cm−2, the electron mobility in these devices is limited by interface charge, whereas for densities above this level, electron mobility is dominated by scattering associated with the AlGaN/GaN interface roughness.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2000
DOI: 10.1109/22.899015
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2008
Publisher: IEEE
Date: 12-2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-1999
DOI: 10.1109/75.774146
Publisher: IOP Publishing
Date: 26-07-2001
Publisher: Springer Science and Business Media LLC
Date: 2000
Publisher: Wiley
Date: 22-06-2010
Publisher: Wiley
Date: 06-2007
Publisher: AIP Publishing
Date: 04-2012
DOI: 10.1063/1.3700246
Abstract: The non-scanning, junction-based photocurrent method is one of many techniques that have been devised to determine the minority carrier diffusion length in semiconductor materials. The accuracy of this method is the subject of this paper and the investigation focuses on the theoretical equation that relates the diffusion length to the measured photocurrent produced by a Schottky barrier diode. Specifically, the investigation concentrates on a commonly used assumption in the derivation of this equation, which is that carriers arriving at the edge of the depletion region are swept away from the depletion edge toward the surface barrier at a velocity that is much greater than the diffusion velocity. The subsequent analysis and the results presented in this paper are based on experiments using p-type GaN. The results obtained from numerical simulations show that both velocities have comparable magnitude and the assumption in question is technically incorrect, especially when the diffusion length is very short, as is common for p-type GaN. However, further analysis also shows that in practice this does not adversely affect the accuracy of the diffusion values calculated. In fact, when the diffusion length is very short, the common equation results in calculated diffusion length values that are more accurate compared to those derived from the more detailed equation. This is an indirect consequence of the choice of the effective depletion width and hence, the relative proportion of the drift and diffusion currents.
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 08-2019
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2000
DOI: 10.1109/55.863096
Publisher: Elsevier BV
Date: 09-2018
Publisher: The Electrochemical Society
Date: 2007
DOI: 10.1149/1.2777007
Publisher: AIP Publishing
Date: 15-11-1999
DOI: 10.1063/1.371602
Abstract: In this article, we discuss parameters influencing (a) the properties of thin AlxGa1−xN layers grown by metalorganic chemical vapor deposition and (b) the electrical properties of the two-dimensional electron gas (2DEG) forming at the AlxGa1−xN/GaN heterojunction. For xAl& .3, the AlxGa1−xN layers showed a strong tendency towards defect formation and transition into an island growth mode. Atomically smooth, coherently strained AlxGa1−xN layers were obtained under conditions that ensured a high surface mobility of adsorbed metal species during growth. The electron mobility of the 2DEG formed at the AlxGa1−xN/GaN interface strongly decreased with increasing aluminum mole fraction in the AlxGa1−xN layer and increasing interface roughness, as evaluated by atomic force microscopy of the surfaces prior to AlxGa1−xN deposition. In the case of modulation doped structures (GaN/AlxGa1−xN/AlxGa1−xN:Si/AlxGa1−xN), the electron mobility decreased with decreasing thickness of the undoped spacer layer and increasing silicon doping. The electron mobility was only moderately affected by the dislocation density in the films and independent of the growth temperature of the AlxGa1−xN layers at xAl=0.3. For Al0.3Ga0.7N/GaN heterojunctions, electron mobility values up to 1650 and 4400 cm2/V s were measured at 300 and 15 K, respectively.
Publisher: IEEE
Date: 12-2014
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 09-2017
DOI: 10.1016/J.ACA.2017.07.066
Abstract: We demonstrate highly selective and sensitive potentiometric ion sensors for calcium ion detection, operated without the use of a reference electrode. The sensors consist of AlGaN/GaN heterostructure-based transistor devices with chemical functionalisation of the gate area using poly (vinylchloride)-based (PVC) membranes having high selectivity towards calcium ions, Ca
Publisher: Springer Science and Business Media LLC
Date: 04-2012
Publisher: Institution of Engineering and Technology (IET)
Date: 1999
DOI: 10.1049/EL:19990627
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 02-2008
Publisher: IEEE
Date: 12-2010
Publisher: Public Library of Science (PLoS)
Date: 11-02-2014
Publisher: IEEE
Date: 12-2010
Location: United States of America
Start Date: 2014
End Date: 2016
Funder: Australian Research Council
View Funded ActivityStart Date: 2005
End Date: 2007
Funder: Australian Research Council
View Funded ActivityStart Date: 2003
End Date: 2005
Funder: Australian Research Council
View Funded ActivityStart Date: 2011
End Date: 2011
Funder: Australian Research Council
View Funded ActivityStart Date: 2009
End Date: 2011
Funder: Australian Research Council
View Funded ActivityStart Date: 2006
End Date: 2006
Funder: Australian Research Council
View Funded ActivityStart Date: 2007
End Date: 2007
Funder: Australian Research Council
View Funded ActivityStart Date: 2007
End Date: 2009
Funder: Australian Research Council
View Funded ActivityStart Date: 2011
End Date: 2011
Funder: Australian Research Council
View Funded ActivityStart Date: 2007
End Date: 2007
Funder: Australian Research Council
View Funded ActivityStart Date: 2012
End Date: 2012
Funder: Australian Research Council
View Funded ActivityStart Date: 2004
End Date: 2009
Funder: Australian Research Council
View Funded ActivityStart Date: 2008
End Date: 2008
Funder: Australian Research Council
View Funded Activity