We aim to achieve a breakthrough in the performance of narrow gap dilute nitride materials that will allow the development of novel mid-infrared photonic devices (especially APDs, LEDs and lasers) to address a range of applications in the technologically important mid-infrared (3-5 µm) spectral range. We envisage wide-ranging impacts through enabling development of new products and procedures that will generate major socio-economic benefits for the UK; scientific advancement leading to substantial generation of new knowledge as well as effective training and professional development of researchers.

Economy

The mid-infrared spectral region contains the unique vibration-band spectral signatures of many compounds. With the benefit of our device-quality dilute nitride materials, we envisage the development of affordable mid-infrared sources and high sensitivity detectors. UK manufacturers will be able to develop new instrumentation to access sizeable new markets for applications including remote gas sensing, range-finding, active imaging and night vision, bio-medical imaging for diagnosis in healthcare and sensitive detection in optical spectroscopy.

We shall foster UK competitiveness and develop impact in this area. Access to device-quality dilute nitrides provides the innovative step that will allow the successful development of the next generation of mid-infrared sources and detectors for these applications. For example, dilute nitrides on GaAs substrates will allow the hybridisation of commercially available read out ICs with low operating voltage InAsN(Sb) APDs, (produced in existing III-V foundries) to yield high performance, cost-effective 2D APD arrays. These will be ideal for integration into vehicle collision avoidance systems (Instro Ltd), also for next generation hand-held eye-safe range-finding and imaging equipment and secure, free space optical communications.

Society

There is a substantial value in environmental monitoring concentrations of greenhouse, toxic and flammable gases such as CO2, CH4 and VOCs over large areas (using DIAL) to map their cycles and identify sources and sinks. Our dilute nitride materials will enable the development of novel mid-infrared sources and detectors for remote sensing and enhanced gas monitoring capabilities over larger areas and from greater distances to achieve better air quality and a positive environmental impact on society.

Mid-infrared imaging is a powerful defence tool in helping to identify concealed explosive threats and is crucial for infrared spectroscopy and for astronomy. However, the cost of current infrared imaging and sensing systems is prohibitively high, due to the cost of cooling requirements. Using larger, cheaper GaAs substrates will reduce array costs, whilst InAsN(Sb) alloys readily allow tuning to the cut-off wavelength of interest, enabling widespread imaging and sensing. We also envisage new MIR LEDs and lasers in instruments for non-invasive measurement of proteins and bio-markers, while superior infrared detection of drugs and bio-agents will enhance security. There are also more immediate applications for 3-5 μm photodiodes and APDs in target ranging and acquisition, secure communications on the battlefield and communications via low orbit satellites with greater up-time than at shorter wavelengths. Hence our research will contribute significantly towards improving air quality, healthcare, safety and national security and defence capabilities.

Knowledge

We shall uncover a wealth of new scientific information which will significantly enhance understanding and impact strongly on the academic community, including fundamental properties of InAsN(Sb); the influence of strain and N/Sb content on defect formation and background doping, MBE growth mechanisms and optimization of growth on GaAs substrates; the resulting effects on radiative and non-radiative recombination, quantum efficiency, gain and excess noise variation with N incorporation, band offsets, effective masses and control of carrier transport and multiplication mechanisms in this unique dilute nitride system.

InAsN(Sb) samples will be provided to our academic and industrial colleagues for complementary studies. Band structure properties obtained from WP2 will improve the understanding of high field transport in III-N-Vs and will be of interest for the design of high speed microwave power devices. Results will be made available for hot electron transport modelling. Photodiodes will be provided to collaborators for assessment in respect of single photon detector development and time-resolved photoluminescence spectroscopy.