Monoclinic β-Ga2O3 microbelts were successfully fabricated using a one-step optical vapor supersaturated precipitation method, which exhibited advantages including a free-standing substrate, prefect surface, and low cost. The as-grown microbelts possessed a well-defined geometry and perfect crystallinity. The dimensions of individual β-Ga2O3 microbelts were a width of ~50 μm, length of ~5 mm, and thickness of ~3 μm. The SEM, XRD, HRTEM, XPS, and Raman spectra demonstrated the high single-crystalline structure of β-Ga2O3 microbelts. Twelve frequency modes were activated in Raman spectra. The optical band gap of the β-Ga2O3 microbelt was calculated to be ~4.45 eV. Upon 266 nm excitation, 2 strong UV emissions occurred in photoluminescence spectra through the radiative recombination of self-trapped excitons, and the blue emission band was attributed to the presence of donor-acceptor-pair transition. The individual β-Ga2O3 microbelt was employed as metal-semiconductor-metal deep-ultraviolet photodetector, which exhibits the photoresponse under 254 nm. This work provides a simple and economical route to fabricate high-quality β-Ga2O3 single-crystal microbelts, which should be a potential synthetic strategy for ultra-wide bandgap semiconductor materials.
Here, we report a strategy to regulate the defect level of zinc vacancy ( VZn) in acceptor-rich ZnO (A-ZnO) microtubes by optical vapor supersaturated precipitation (OVSP) combined with the first-principles calculation. The formation energy (FE) of VZn in ZnO is calculated based on the density functional theory, indicating the FE of VZn depending upon the surrounding Zn chemical potential in ZnO. The defect level of VZn is experimentally controlled in the A-ZnO microtubes by regulating the concentration of oxygen during the OVSP process. For the high oxygen concentration, the photoluminescence intensity of VZn-related donor–acceptor pair emission is enhanced by 46%, compared with those grown in oxygen-deficient conditions. Meanwhile, a defective 2LA mode appeared in the Raman spectra of A-ZnO microtubes with the increase in oxygen concentration, confirming the controllability of the generation of VZn. The VZn defects induce the conductive filaments for the resistive switching behavior in the A-ZnO microtubes, by which the on/off ratio can be enhanced by up to ∼103. Moreover, the tunable current-induced thermal tunneling electroluminescence was also realized by the defect-controlled A-ZnO microrods/tubes. This work opens new opportunities for the design of novel optoelectronic devices by defect-engineered wide-bandgap semiconductors in future.
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