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• Decoration of Bi 2 Se 3 on laser molecular beam epitaxy-grown GaN nanostructures. • Bi 2 Se 3 /GaN heterojunction showed high ultra-violet photodetector responsivity. • Heterojunction Bi 2 Se 3 /GaN for dual-wavelength photodetector applications. Recently, highly responsive photodetectors which are capable of photodetection in a wide range of wavelength spectra are in great demand. To fulfil this, photodetectors formed using heterojunctions of multiple semiconducting materials gain a lot of interest as they cover a broad range of photodetection, and the built-in electric field developed at their interface helps to enhance photoresponse. Here, we have demonstrated a fascinating broadband metal-semiconductor-metal type photodetector (PD) by integrating sputtered Bi 2 Se 3 with the laser molecular beam epitaxy (LMBE) grown GaN film and porous nanowall network on sapphire (0001) substrates. The fabricated photodetectors using a hybrid Bi 2 Se 3 /LMBE-GaN nanowall structure exhibit broadband characteristics with a high responsivity of 51.4 and 1.46 A/W when illuminating with the laser of wavelength 355 nm (UV) and 1064 nm (NIR), respectively. The enhanced UV responsivity and good response in the NIR region using Bi 2 Se 3 /GaN heterojunction nanostructures suggest futuristic application in dual-wavelength detector devices. [Display omitted] [ABSTRACT FROM AUTHOR]

We report the direct growth of self-aligned single crystalline GaN nanorod array on flexible Ta metal foil using laser molecular beam epitaxy. Scanning electron microscopy reveals the vertically aligned nanorods on Ta surface having diameters in the range of 60–80 nm. The nanorods show well-defined hexagonal facets and are quite uniformly distributed across the metal foil. Transmission electron microscopy shows single crystalline nature of the individual rods having c-axis oriented growth with wurtzite structure. Room temperature photoluminescence study exhibits a sharp, intense band-to-band emission without any deep-level bands indicating the excellent optical quality of the GaN nanorod array. X-ray photoemission spectroscopy to elucidate the electronic structure of the nanorods confirms Ga–N bonding and the calculated chemical composition turns out to be slightly Ga rich. Location of valence band maxima also suggests the n -type character of GaN nanorods. The photoelectrochemical water-splitting behaviour of the self-aligned GaN nanorod arrays on Ta foil has been investigated using 1 M oxalic acid as the electrolyte with AM 1.5 G simulated solar radiation under 1 Sun (100 mW/cm2) conditions. The results demonstrate an effective way of fabricating well-aligned GaN nanorods on flexible metal foils for developing simple, relatively inexpensive, and flexible photo-electrodes for photocatalytic solar water-splitting applications. • Direct growth of vertically self-aligned GaN nanorod array on Ta foil is achieved. • The nanorods are single crystalline and have a high density of 1.4–2 × 1010 cm−2. • They exhibit a narrow and intense band-edge emission with negligible defect bands. • Solar water-splitting property of GaN nanorod array on Ta foil is demonstrated. [ABSTRACT FROM AUTHOR]