Nanomesh electrode on MgZnO-based metal-semiconductor-metal ultraviolet photodetectors
Ching-Ting Lee1, Heng-Yu Lin1, Chun-Yen Tseng1
1Institute of Microelectronics, Department of Electrical Engineering, Research Center of Energy Technology and Strategy, and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan, Republic of China.
Abstract:
In this work, the nano-scaled mesh electrodes are fabricated by obliquely depositing metals through the highly ordered polystyrene nanosphere mask. Furthermore, the intrinsic MgZnO film is deposited as the absorption layer for the metal-semiconductor-metal ultraviolet photodetectors (MSM-UV-PDs) using the vapor cooling condensation system. The 100-nm-linewidth nanomesh electrodes with metal occupying a roughly 10% of the device surface region consequently render PDs with a high transmittance in the ultraviolet (UV) wavelength range. The photoresponsivity of MgZnO-based MSM-UV-PDs evaluated at the wavelength of 330 nm with the operating bias voltage of 5 V is elevated from 0.135 to 0.248 A/W when the thin metal electrode is replaced by the nanomesh electrode, and the corresponding quantum efficiency is improved from 50.75 to 93.23%. Finally, adopting the nanomesh electrode also helps to enhance the UV-visible rejection ratio (R330nm/R450nm) and the detectivity from 1663 and 1.78 × 10(10) cmHz(0.5)W(-1) to 2480 and 2.43 × 10(10) cmHz(0.5)W(-1), respectively.
