Periodic Reporting for period 2 - PROMIS (Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics)
Reporting period: 2017-01-01 to 2018-12-31
Work Package 2: APDs with low dark current were realized at SHEFF by addition of Ga to the very thin AlGaAsSb avalanche layer which reduced the surface leakage current, (with lifetimes measured at Tyndall-UCC), without any significant band to band tunnelling. A new etchant was developed for InGaAs-AlGaAsSb APDs which produced more uniform dark current. The AlGaAsSb APDs were significantly more tolerant to temperature fluctuation than commercial APDs. Gallium nanoparticle layers were deposited on top of InGaAs APDs by UAM which improved their sensitivity. New methods for the production of colloidal Ga nanoparticles were also developed which exhibit tunability and strong plasmonic absorption in the UV, depending on the nanoparticle dimensions and aggregation state. A particular highlight was the first high speed, fully integrated Quantum Random Number generator chip demonstrated by IDQuantique and TUDelft, leading to an innovative Quanta Image Sensor with Dartmouth College, for which a patent is filed.
Work Package 3: Both tandem and intermediate band solar cells were studied. III-V Lab advanced the state of the art of InP-based solar cells grown by MOVPE using a novel tunnel junction. InP and InGaAs single junction cells grown on InP showed efficiencies of 13.5% and 11.4%, respectively, while the InP/InGaAs tandem cell exhibited a conversion efficiency of 18.3%. The same architecture was grown and validated on a commercial InP/Si template. GaSb single-junction solar cells grown by MBE on GaSb at UM exhibited state of the art performance with 5.9% efficiency. The first AlInAsSb/GaSb tandem solar cells were successfully fabricated, with efficiency limited by the top cell. ULANC (with TEM at UCA) demonstrated type II intermediate band solar cells containing 40 layers of GaSb quantum rings - the highest reported to date - without introducing additional dislocations, resulting in enhancement of sub-bandgap absorption and partial VOC recovery under concentration (4000 suns).
Work Package 4: Nanostructures with improved quantum confinement enabled fabrication of brighter, more efficient LEDs for C-H and CO2 detection on GaAs substrates using new metamorphic buffer layers for widespread uptake. ULANC realised mid-infrared LEDs with internal efficiency of 10% , validated by GSS for gas sensors. NOTT discovered a new type of Zener tunnelling in InAsN/InAlAs diodes mediated by N-related zero-dimensional states. One highlight was the laser patterning of plasmonic structures with micrometer spatial resolution by dissociation of the N-H bond in hydrogenated In(As,N), enabling a new, compact, low-cost scalable technology for exploitation in security, environmental control, pharmaceuticals, etc. UM developed new techniques for bio-functionalization of III-V surfaces and surface-enhanced vibrational spectroscopy. By exploiting the change in refractive index upon oxidation the localized plasmon resonance of InAsSb:Si gratings on GaSb was tuned from 5 to 20 μm. In collaboration with Sikémia, the controlled chemical bonding of organic molecules to the III-V semiconductor surface by phosphonic acid chemistry led to new methods for bio-sensing to be patented.