Defect controlled ultra high ultraviolet photocurrent gain in Cu-doped ZnO nanorod arrays: De-trapping yield

Abstract

Understanding the mechanism behind high photocurrent gain is very important to realize a highly functional material for photodetector devices. Herein, we report a very high ultraviolet photocurrent gain of 2.8 × 105 in hydrothermally grown Cu-doped ZnO nanorod arrays which is two orders of magnitude higher as compared to the undoped sample. Trapping of carriers under dark and de-trapping them under illumination by Cu-related defects is responsible for high gain. The trap state at ∼1.65 eV is attributed to the [{CuZn+(3d10)}− − Zni+(4s1)]0 type of defects. A model is shown to explain the dark and photocurrent states in the doped samples.

Doped ZnO 1D Nanostructures: Synthesis, Properties, and Photodetector Application

“…The UV photodetectors used the multiple 1D‐NSs method. Figure (a) and (b) reveal the photocurrent spectra and UV on/off functional switching of the Cu‐doped ZnO and pure ZnO 1D‐NSs . The photocurrent spectra allow sufficient time to show the de‐trapping yield, and this and an X‐ray photoelectron spectroscopy (XPS) spectrum of a 2% Cu‐doped sample are shown in Figure (c) and (d), respectively.…”

“…A higher photocurrent gain has been achieved by different methods, such as decreasing the dark current and increasing the photocurrent and absorption cross section of the material. S. Sarkar et al reported the growth of a ZnO seed layer on a glass substrate via a DC magnetron sputtering technique, and a 2% Cu‐doped ZnO nanorod array on a substrate via a hydrothermal method . The UV photodetectors used the multiple 1D‐NSs method.…”

“…In this section, we will review recent articles about doped ZnO 1D-NS photodetectors, and provid an overview of the optical properties and measured results which are briefl y summarized in Table 3 . [146][147][148][149][150][151][152][153][154][155][156][157][158][159][160] The performance of doped ZnO 1D-NS photodetectors is greatly superior to ZnO or doped ZnO thin fi lm photodetectors, but it still cannot compare to conventional top-down fabricated GaN-based photodetectors due to a very slow photoresponse time. So far, many research groups have been trying to increase the photocurrent gain (I photo / I dark ratio) and decrease the photoresponse time of doped ZnO 1D-NS photodetectors, and different methods have been studied to improve their performance.…”

“…S. Sarkar et al reported the growth of a ZnO seed layer on a glass substrate via a DC magnetron sputtering technique, and a 2% Cu-doped ZnO nanorod array on a substrate via a hydrothermal method. [ 151 ] The UV photodetectors used the multiple 1D-NSs method. Figure 10 (a) and (b) reveal the photocurrent spectra and UV on/off functional switching of the Cu-doped ZnO and pure ZnO 1D-NSs.…”

“…Figure 10 (a) and (b) reveal the photocurrent spectra and UV on/off functional switching of the Cu-doped ZnO and pure ZnO 1D-NSs. [ 151 ] The photocurrent spectra allow suffi cient time to show the de-trapping yield, and this and an X-ray photoelectron spectroscopy (XPS) spectrum of a 2% Cu-doped sample are shown in Figure 10 (c) and (d), respectively. It can be seen that the UV photocurrent gain of these Cu-doped ZnO nanorods could reach 2.8 × 10 5 (I photo = 23 µA/I dark = 85 pA), which is around 2 orders of magnitude larger than that observed from the pure ZnO nanorods.…”