Self‐Polarized BaTiO₃ for Greatly Enhanced Performance of ZnO UV Photodetector by Regulating the Distribution of Electron Concentration

Abstract

ZnO film ultraviolet photodetectors (UV PDs) have always suffered from slow speed and low photosensitivity that restrict their broader applications. To break through those barriers, high-performance ZnO UV PD based on self-polarized BaTiO 3 (BTO) is first introduced through a facile one-step spin-coating method. Compared with pure ZnO film UV PD with low on/ off ratio (65) and slow speed (4.1/7.5 s) at 3 V bias under 350 nm UV light, the BTO-ZnO bilayer film device exhibits an ultrahigh on/off ratio (14 300) and ultrafast response speed (0.11/5.80 ms), which is much faster than that of the most reported ZnO film-based UV PDs. The numerical simulation demonstrates that the spatial distribution of electron concentration of ZnO film is regulated by the self-polarization of BTO film, resulting in low dark current and fast response time of the BTO-ZnO PD. This work provides a new approach to fabricate high-performance PDs based on self-polarized ferroelectric materials.

Depolarization electric field and poling voltage‐modulated Pb,La(Zr,Ti)O3‐based self‐powered ultraviolet photodetectors

“…The rise time (t r ) and decay time (t d ) are defined as the time it takes for the photocurrent to increase from 10% to 90% and decrease from 90% to 10% of the maximum value, respectively. 3,17,35 As can be seen from the figures, the t r /t d of the PDs with different Ti contents is estimated as 62/116 ms, 75/150 ms, 28/38 ms, 18/34 ms, 18/28 ms, respectively. Obviously, the higher the Ti content in the PLZT film, the faster the response speed of the PD, and when the Ti content is more than 75 mol%, all devices show a fairly fast response speed.…”

“…Figure 6A‐E shows the time‐dependent photoelectric response characteristics of the PLZT‐based PDs with various Ti contents under their respective maximum poling voltages and a single UV illumination period. The rise time ( t r ) and decay time ( t d ) are defined as the time it takes for the photocurrent to increase from 10% to 90% and decrease from 90% to 10% of the maximum value, respectively 3,17,35 . As can be seen from the figures, the t r / t d of the PDs with different Ti contents is estimated as 62/116 ms, 75/150 ms, 28/38 ms, 18/34 ms, 18/28 ms, respectively.…”

“…To show the sensitivities of photoelectric responses to optical stimuli, the responsivity ( R ) of the PDs with various Ti contents and positive poling voltages is given in Figure 4A‐E R is defined as the amount of current converted per unit of radiation power and is expressed by the following Equation (): 3,32,33 where I light is the photocurrent, I dark is the dark current, P λ is the light intensity at each wavelength, and S is the effective illumination area ( S = 0.05 × 0.05 cm 2 in this work). As the Ti content increases from 40 mol% to 87.5 mol%, the maximum R improves from 0.16 mA/W to 4.17 mA/W, and with the increase in the positive poling voltage, the R continuously improves.…”

“…Ultraviolet (UV) photodetectors (PDs) have recently received substantial attention because of their use in a variety of applications, such as environmental protection, flame detection, missile warning systems, space communication, chemical and biological sensing, remote control, etc [1][2][3][4][5][6] In commonly used UV PDs, which are prepared from wide band-gap semiconductor materials (eg, ZnO, SiC, SnO 2 , TiO 2 , and GaN), [7][8][9] photogenerated electrons and holes are separated by an external applied electric field and thus external power sources and supplies are required. This limits the suitability of such PDs for device miniaturization and integration.…”

A High‐Photocurrent and Fast‐Response Polarity‐Controlled ZnO‐Based UV Photodetector Grown by a Sol–Gel Process

“…[ 1–5 ] ZnO films, among several optoelectronic devices, have attracted attention as UV light detection devices owing to their wide direct bandgap energy (≈3.4 eV). [ 6–11 ] Fast response/recovery times, high responsivity, high reliability, and low noise are important characteristics of photodetectors (PDs). [ 12,13 ] High‐performance ZnO‐based PDs were achieved using a ZnO film in the (002) plane along the c ‐axis on a c ‐plane sapphire substrate.…”