Synthesis and Optical Characterization of a High-quality (111) ZnS Crystal for UV-optoelectronics Device
Min-Han Lin1*, Ching-Hwa Ho1
1Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, Taiwan
* presenting author:Min-Han Lin,
ZnS is an environmental-friendly wide-band-gap semiconductor which possessing a direct gap larger than ZnO. It’s more promising for application in ultraviolet (UV) optoelectronics and solar-energy conversion. However, highly crystalline ZnS is usually obtained by elegant epitaxial growth like pulsed laser vaporization, molecular beam epitaxy, and metalorganic chemical vapor deposition with a thin-film form. A high-quality ZnS substrate crystal was rarely found to date. We demonstrate, herein, a high-grade cubic ZnS (111) plane substrate crystal of longer range order grown by chemical vapor transport (CVT) method. The thermoreflectance (TR), photoluminescence (PL) and transmission electron microscopy are implemented for qualification of the ZnS (111) plane substrate. A strong and complete series excitonic transition has been detected from the ZnS substrate crystal by TR, and indicating high crystallinity of the CVT-grown ZnS. The band-edge transitions of the ZnS substrate shows intense around 3.75 eV at 300 K. Temperature dependences of the band-edge transitions from 30K to 300 K have been analyzed and discussed to sustain high crystalline quality of the ZnS (111) plane substrate. All the experimental analyses show that the TR and PL measurements are powerful techniques for optical characterization of structure and optoelectronics properties of the cubic ZnS (111) crystal. It is suitable for ultraviolet (UV) optoelectronics use.

Keywords: semiconductor, thermoreflectance, photoluminescence, substrate, ultraviolet optoelectronics