Light wavelength identification is essential for many optical and optoelectronic applications. Here, we report a novel wavelength identification photodetector based on the energy distribution of hot electrons at the metal/insulator interface. The information of the light wavelength can be stored in the energy distribution of the hot electrons, which can then be readout in the form of the current–voltage characteristics. On the basis of this principle, the high-reliability wavelength identification of the monochromatic light has been realized with a simple Al/SiO2/Si structure. The device has an excellent stability with dark current below 1 × 10–7 A/m2. Moreover, the wavelength of the monochromatic light in the deep ultraviolet range can be identified. This new principle will pave a new solution to design high-performance single-chip wavelength identification photodetectors and integrated miniaturized wavelength identification systems.Topics: Electric transport processes and properties; Energy; Materials science; Solid state electrochemistry;

Photodetectors for the ultraviolet (UV) range of the electromagnetic spectrum are in great demand for several technologies, but require the development of novel device structures and materials. Here we report on the high detectivity of UV photodetectors based on well-ordered laterally mesoporous GaN. The specific detectivity of our devices under UV-illumination reaches values of up to 5.3 × 1014 Jones. We attribute this high specific detectivity to the properties of the mesoporous GaN/metal contact interface: the trapping of photo-generated holes at the interface lowers the Schottky barrier height thus causing a large internal gain. High detectivity along with a simple fabrication process endows these laterally mesoporous GaN photodetectors with great potential for applications that require selective detection of weak optical signals in the UV range.

GaN-based nanoporous green LEDs with different pore depth have been fabricated by using anodic aluminum oxide (AAO) as dry etching mask. The experimental results show that the electrical properties of the nanoporous LEDs with different pore depths are similar, but for the optical properties, the LEDs with nanopores extended to the p-GaN layer exhibits the best performance, if increase the depth to MQWs or decrease to the ITO layer will both decrease the light output power (LOP). By calculating the light extraction efficiency using three-dimensional (3D) finite-difference time-domain method, the decrease of the light output is mainly attributed to the reduced light extraction efficiency when the pore depth stop at ITO transparent layer instead of p-type layer, while if the depth reach the MQWs, the deterioration of the QWs which is caused by dry etching damage will play an important role. This optimization would give a valuable guidance to the surface structure design for nanostructured GaN-based LEDs, such as surface roughening, photonic crystal, or top-down fabricated surface-plasmon enhanced LEDs.

The optical properties of e-shape plasmonic nanocavities have been studied. Due to the destructive interference of the quadrupole resonance of the c-shape nanoring with the overlapping dipolar resonance of the nanorod, a tunable Fano resonance within a wide range of spectra from visible light to mid-infrared (mid-IR) spectrum have been observed. The spectral positions and modulation depths of the Fano resonances can be tuned with different geometry parameters of nanocavities, and the performance (modulation depth of spectra and near-field enhancement) of e-shape plasmonic nanocavities can be further improved by optimization of the nanocavity’ radiation characteristics using a dielectric layer (SiO2). Furthermore, capacitive coupling between c-shape nanoring and nanorod antenna was found to be asymmetric, in which Fano resonance can be modulated to symmetric/antisymmetric quadrupole–dipole by moving the nanorod in the positive/negative direction of the x axis. This work opens up new opportunities for engineering spectral features and optimizing performance of a broad range of plasmonics devices.