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In the last decade, interest in the use of beta gallium oxide (β-Ga2O3) as a semiconductor for high power/high temperature devices and deep-UV sensors has grown. Ga2O3 has an enormous band gap of 4.8 eV, which makes it well suited for these applications. Compared to thin films, nanowires exhibit a higher surface-to-volume ratio, increasing their sensitivity for detection of chemical substances and light. In this work, we explore a simple and inexpensive method of growing high-density gallium oxide nanowires at high temperatures. Gallium oxide nanowire growth can be achieved by heating and oxidizing pure gallium at high temperatures (~ 1000 °C) in the presence of trace amounts of oxygen. This process can be optimized to large-scale production to grow high-quality, dense and long Ga2O3 nanowires. We show the results of morphological, structural, electrical and optical characterization of the β-Ga2O3 nanowires including the optical bandgap and photoconductance. The influence of density on these Ga2O3 nanowires and their properties will be examined in order to determine the optimum configuration for the detection of UV light.

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In this study, a detailed experimental and theoretical investigation of optical absorption properties of indium sulfi de (In 2 S 3 ) nanostructure arrays in different shapes are presented. Zigzags, springs, screws, tilted rods, and vertical rods of In 2 S 3 are grown using a glancing angle deposition (GLAD) technique. Nanostructured coatings are of similar material volume and porosity, yet with different shapes. Total optical refl ection, transmission, and absorption profi les of In 2 S 3 nanostructures are obtained by UV-vis-NIR spectroscopy using an integrating sphere. Measurements reveal that optical absorption of semiconducting nanostructures can strongly depend on their shapes. Under normal incidence of light, 3D geometries such as springs, screws, and vertical rods can provide enhanced absorption compared to zigzags, and tilted rods. Results of fi nite difference time domain (FDTD) simulations predict that spring, screw, and tapered-rod shapes can introduce a uniform distribution of diffracted light intensity and stronger absorption within the nanostructured layer, indicating an enhanced diffuse light scattering and light trapping.Zigzags and tilted rods show a relatively weaker absorption, similar to the experimental results. Experimental and simulation results are also compared to the predictions of effective medium theory. Current effective medium approximations are not suffi cient to explain the high optical absorption of the nanostructures.Adv. Optical Mater. 2013, 1, 158-166 159 wileyonlinelibrary.com

Enhancing photon detection efficiency and time resolution in photodetectors in the entire visible range is critical to improve the image quality of time-of-flight (TOF)-based imaging systems and fluorescence lifetime imaging (FLIM). In this work, we evaluate the gain, detection efficiency, and timing performance of avalanche photodiodes (APD) with photon trapping nanostructures for photons with 450 nm and 850 nm wavelengths. At 850 nm wavelength, our photon trapping avalanche photodiodes showed 30 times higher gain, an increase from 16% to >60% enhanced absorption efficiency, and a 50% reduction in the full width at half maximum (FWHM) pulse response time close to the breakdown voltage. At 450 nm wavelength, the external quantum efficiency increased from 54% to 82%, while the gain was enhanced more than 20-fold. Therefore, silicon APDs with photon trapping structures exhibited a dramatic increase in absorption compared to control devices. Results suggest very thin devices with fast timing properties and high absorption between the near-ultraviolet and the near infrared region can be manufactured for high-speed applications in biomedical imaging. This study paves the way towards obtaining single photon detectors with photon trapping structures with gains above 106 for the entire visible range.