arXiv subjects

Richard J. Curry

Publications and source records attributed to Richard J. Curry.

7 recordsLinked to original sources

arXiv2026

Dose-Insensitive Defect Engineering, Carrier Kinetics, and Reproducible Chromaticity Tuning in Ion-Implanted InGaN/GaN Quantum Wells

Post-growth defect engineering via ion implantation provides a powerful pathway for spatial optical profiling and colour patterning in III-V alloying photonic integration. However, the comprehensive recombination kinetics governing deep-level defect saturation and excitonic recovery under high-temperature annealing remain insufficiently understood. Here, we present a systematic study on the optical dynamics, rate-equation kinetics, and chromaticity evolution of indium-implanted InGaN/GaN multiple quantum wells (MQWs) across implantation doses (5E14 to 5E16 ions cm^-2) and subsequent thermal annealing stages (500 to 1100 deg C). Photoluminescence (PL) spectrum analysis reveals that a dose of <= 5E14 ions cm^-2 induces a modification of the optical response that does not further change upon high-dose implantation. A two-channel coupled rate-equation model is fitted to the data, optimised via differential evolution, allowing the extraction of transition rate constants. This demonstrates that thermal processing at 1000 deg C suppresses the carrier capture rate into deep-level states and also reduces its radiative recombination rate. This kinetic bottleneck drives an order-of-magnitude extension in the channel-specific radiative lifetime. Leveraging the excitation power density dependence of the differential recombination kinetics, where deep defects saturate whilst MQW emission scales near-linearly, we achieve a universal and power density-tunable chromaticity trajectory from warm yellow to cool white-blue emission. These insights enable microscopic defect physics to be linked to the macro-scale colour tailoring observed.

physics.app-ph↗

arXiv2026

Thermal Stability and Carrier Recombination Kinetics in InGaN/GaN Multiple Quantum Wells under High-Temperature Annealing

The thermal stability and carrier recombination kinetics of an as-received InGaN/GaN multiple quantum well (MQW) structure, capped with a protective AlN thin film, are studied following a series of thermal annealings at temperatures between 500 deg C and 1100 deg C. Under 325 nm focused laser excitation at room temperature, the sample's photoluminescence (PL) spectrum exhibits three emission bands: an ultraviolet peak at 363 nm, a blue peak at 455 nm, and a yellow peak at 565 nm. We find that the MQW's 455 nm emission is preserved after annealing at 1100 deg C. Moreover, room-temperature PL excitation (PLE) and time-resolved PL (TRPL) have been investigated to shed light on the sample's energy-transfer mechanisms and emission decay characteristics. Power-dependent PL spectra analysis shows that the carrier recombination mechanism of the MQW's emission has not been affected by thermal treatment. Rate equation modelling and chromaticity coordinate analysis also show limited thermal impact on the calculated equivalent emission lifetime and emissive colour. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis has been performed, further evidencing the preservation of the MQW structure in the annealed sample.

physics.app-ph↗

arXiv2026

Electrically detected magnetic resonance of $^{75}$As magnetic clock transitions in silicon

Magnetic clock transitions (CTs), defined by vanishing first-order sensitivity of the transition frequency to magnetic field fluctuations, provide a powerful route to suppress decoherence in donor spin systems. Here, we present the observation of magnetic field CTs from an ensemble of near-surface $^{75}$As ($I = 3/2$) spins in silicon using low-field ($< 10$~mT) continuous-wave electrically detected magnetic resonance (EDMR). As the CT condition is approached, pronounced linewidth broadening is observed, consistent with a donor Hamiltonian informed linewidth model. These results establish low-field EDMR as a sensitive probe of CTs in near-surface donor systems relevant to silicon-based quantum devices.

quant-ph↗

arXiv2023

Highly ${ }^{28} \mathrm{Si}$ Enriched Silicon by Localised Focused Ion Beam Implantation

Solid-state spin qubits within silicon crystals at mK temperatures show great promise in the realisation of a fully scalable quantum computation platform. Qubit coherence times are limited in natural silicon owing to coupling to the isotope ${ }^{29} \mathrm{Si}$ which has a non-zero nuclear spin. This work presents a method for the depletion of ${ }^{29} \mathrm{Si}$ in localised volumes of natural silicon wafers by irradiation using a 45 keV ${ }^{28} \mathrm{Si}$ focused ion beam with fluences above $1 \times 10^{19} \, \mathrm{ions} \, \mathrm{cm}^{-2}$. Nanoscale secondary ion mass spectrometry analysis of the irradiated volumes shows unprecedented quality enriched silicon that reaches a minimal residual ${ }^{29} \mathrm{Si}$ value of 2.3 $\pm$ 0.7 ppm and with residual C and O comparable to the background concentration in the unimplanted wafer. Transmission electron microscopy lattice images confirm the solid phase epitaxial re-crystallization of the as-implanted amorphous enriched volume extending over 200 nm in depth upon annealing. The ease of fabrication, requiring only commercially available natural silicon wafers and ion sources, opens the possibility for co-integration of qubits in localised highly enriched volumes with control circuitry in the surrounding natural silicon for large-scale devices.

cond-mat.mtrl-sci↗

arXiv2020

Power and spectral characterization of photonic integrated circuit based axicon like lens

We demonstrate an on-chip Silicon-on-Insulator (SOI) axicon etched using a low resolution (200 nm feature size, 250 nm gap) deep-ultraviolet lithographic fabrication. The axicon consists of circular gratings with seven stages of 1x2 multimode interferometers. We present a technique to apodize the gratings azimuthally by breaking up the circles into arcs which successfully increased the penetration depth in the gratings from $\approx$5 $μ$m to $\approx$55 $μ$m. We characterize the device's performance by coupling 1300$\pm$50 nm swept source laser in to the chip from the axicon, and measuring the out-coupled light from a grating coupler. Further, we also present the implementation of balanced homodyne detection method for the spectral characterization of the device and show that the position of the output lobe of the axicon does not change significantly with wavelength.

physics.optics↗

arXiv2014

Electrical properties of Bi-implanted amorphous chalcogenide films

The impact of Bi implantation on the conductivity and the thermopower of amorphous chalcogenide films is investigated. Incorporation of Bi in Ge-Sb-Te and GeTe results in enhanced conductivity. The negative Seebeck coefficient confirms onset of the electron conductivity in GeTe implanted with Bi at a dose of 2x1016 cm-2. The enhanced conductivity is accompanied by defect accumulation in the films upon implantation as is inferred by using analysis of the space-charge limited current. The results indicate that native coordination defects in lone-pair semiconductors can be deactivated by means of ion implantation, and higher conductivity of the films stems from additional electrically active defects created by implantation of bismuth.

cond-mat.mtrl-sci↗

arXiv2014

n-Type Chalcogenides by Ion Implantation

Carrier-type reversal to enable the formation of semiconductor p-n junctions is a prerequisite for many electronic applications. Chalcogenide glasses are p-type semiconductors and their applications have been limited by the extraordinary difficulty in obtaining n-type conductivity. The ability to form chalcogenide glass p-n junctions could improve the performance of phase-change memory and thermoelectric devices and allow the direct electronic control of nonlinear optical devices. Previously, carrier-type reversal has been restricted to the GeCh (Ch=S, Se, Te) family of glasses, with very high Bi or Pb doping concentrations (5 to 11 at.%) incorporated during high-temperature glass melting. Here we report the first n-type doping of chalcogenide glasses by ion implantation of Bi into GeTe and GaLaSO amorphous films, demonstrating rectification and photocurrent in a Bi-implanted GaLaSO device. The electrical doping effect of Bi is observed at a 100 times lower concentration than for Bi melt-doped GeCh glasses.

cond-mat.mtrl-sci↗