Aluminum gallium nitride (Al x Ga 1−x N) alloy films and nanostructures have attracted extensive research attention for ultraviolet (UV) and deep ultraviolet optoelectronic applications. However, the morphology-controlled growth of high-quality Al x Ga 1−x N quasi one-dimensional nanostructures has been limited by the complex multicomponent phase diagram and inhomogeneous composition distribution. Here, we demonstrated the growth of Si-doped ntype compositionally uniform Al 0.45 Ga 0.55 N nanorods employing a metal organic chemical vapor deposition (MOCVD) technique for the application in UV-C photodetectors. A two-step growth process, namely, growth of undoped GaN seeds and subsequent growth of n-AlGaN nanorods over GaN seeds, has been developed. Various characterization techniques have been used to study the crystalline quality, orientation, and optical properties of the realized nanorods. Field emission scanning electron microscopy revealed a uniform distribution of vertically aligned n-AlGaN nanorods over the GaN seeds. X-ray diffraction studies showed that the grown nanorods are preferentially (0002) oriented with hexagonal crystal structure. High-resolution transmission electron microscopy images indicated the nanorods are single crystalline in nature, without any significant crystalline defects and dislocations. Cathodoluminescence spectra of AlGaN nanorods displayed a strong band edge excitonic emission peak at 276 nm at 77 K and shifted to lower energy as the temperature increased to 300 K. The photocurrent current (I p ) of the fabricated photoconductive device was significantly higher in the UV region (250−276 nm) compared to the corresponding dark current. The photocurrent displayed a nonlinear power density (P)-dependent characteristics (I p ∝ P 0.64 ). The photoresponsivity and sensitivity of the fabricated photodetector were estimated to be ∼115 mA/W and ∼64%, respectively, in the UV-C region.

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This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased.

CIGS solar cells fabricated with different types of AZO/metal/AZO (AZO/Cu/AZO, AZO/Mo/AZO and AZO/Cu–Mo/AZO) transparent conducting electrodes.

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