Optical and Optoelectronic Performances of Quasi-Rectangular Cross-Sectional Sn-Doped CdS Nanowires

The morphology of the end facet has a great effect on the performance of the one-dimensional semiconductor nanostructure. In terms of the lattice structure, the end facet of synthesized CdS nanostructures is usually hexagonal-shaped. Therefore, morphological tunability of the end facet for CdS is still a challenge. In this work, quasi-rectangular cross-sectional Sn-doped CdS nanowires were successfully synthesized by the chemical vapor deposition method. The crystal and morphological properties of synthesized nanowires were characterized by transmission electron microscopy and scanning electron microscopy. Because of the high crystal quality and well-cleaved surface, optically pumped whispering gallery mode lasing is realized at room temperature with a threshold of 11.3 mW/cm2. Compared to the hexagonal-shaped Sn-doped CdS nanowires, the tunability of the output mode is achieved. Temperature-dependent photoluminescence spectra were measured, and the temperature coefficient is determined to be -0.515 meV·K-1. In addition, the activation energy was fitted to be 43.01 meV, illustrating that the main carrier decay channel exhibits exciton recombination. The quasi-rectangular cross-sectional Sn-doped CdS nanowire-based photodetectors presented a maximum current on/off ratio of 3 × 102. The photoresponsivity and specific detectivity were estimated to be 0.22 mA/W and of 1.14 × 1012 Jones under the illumination of 405 nm laser with a laser density of 495 μW/cm2 at VDS = 3 V. Moreover, n type doping behavior is determined by the field effect transistor device, and the field effect mobility is calculated to be 0.18 cm2·V-1·s-1. Our work provides a new way to tailor the properties of CdS for the application in integrated photonic and optoelectronic devices.