Recently, there has been a surge of interest in the wide bandgap semiconductors for solar blind photo detectors (SBPD). This work presents our recent progress in the growth/doping of AlGaN and Ga2O3 thin films for solar blind detection applications. Both of these thin films grown are grown by metal organic chemical vapor deposition (MOCVD) in the same Aixtron MOCVD system. Solar-blind metal-semiconductor-metal photodetectors were fabricated with Ga2O3. Spectral responsivity studies of the MSM photodetectors revealed a peak at 261 nm and a maximum EQE of 41.7% for a −2.5 V bias. We have also demonstrated AlGaN based solar-blind avalanche photodiodes with a gain in excess of 57,000 at ~100 volts of reverse bias. This gain can be attributed to avalanche multiplication of the photogenerated carriers within the device. Both of these devices show the potential of wide bandgap semiconductors for solar blind photo detectors.
We present a novel design for an axisymmetric, three-dimensional tapered dome shaped nanoantenna structure similar to nanocones. The proposed design is modelled and analyzed using numerical simulation employing the finite element method (FEM) on COMSOL. Tapered structures have emerged as promising devices in efficiently guiding and localizing free-space radiation near the apex when excited by an external electric field, thus promoting a stronger light–matter interaction. Such metallic vertically tapered structures similar to nanocones provide strong filed enhancement at the tip when the resonance condition is fulfilled and hence most design applications of such structures rely on excitation produced at the tip. In this study the traditional nanocone structure is modified to form a tapered minaret structure comprised of multiple layers and an onion-shaped crown. Enhancement factors of the order of 104 are obtained at the tip at resonance with high directivity, thus providing an accessible hot spot. These features make the structure particularly suitable for use as nanoprobes for tip-enhanced Raman spectroscopy (TERS), scanning nearfield optical microscopy (SNOM), and surface plasmon polaritons enhanced Raman scattering (SPPERS).
Photonic Crystal Fibers have proved to be an efficient medium for propagation of electromagnetic radiation especially in the Terahertz regime. Located between the infra-red and microwave region, the Terahertz frequency range lies within 0.1 to 1 Terahertz. We report a design of a graduating ring rectangular-core Photonic Crystal Fiber, having background material as Cyclic-Olefin Copolymer (COC), with extremely low confinement loss of 4.9399 × 10−7 dB/cm and material loss of 0.2 cm−1 at 0.22 mm pitch value. Due to the very low loss values, such a structure of the Photonic Crystal Fiber can be used for efficient low-loss data communication.