Avalanche Effect and High External Quantum Efficiency in MgZnO/Au/ZnO Sandwich Structure Photodetector

Abstract

MSM structure is widely applied to PD owing to its relatively simple preparation methods, short response time, and more effective light collecting area. However, MSM PD poses significant challenges that are mainly related to the external quantum efficiency (EQE) and weak light detection, owing to the optical loss of incident light by electrode shielding and the necessity of applying a bias voltage for device operation. To increase the EQE of PDs and probe weak signals, extensive research efforts have been devoted to the study on EQE of MSM PD in recent years. The research on avalanche effect has received extensive attention owing to its excellent low-light detection capability. [11][12][13][14] Under normal conditions, the avalanche effect is usually realized by p-n or p-i-n photodiodes because of the realization of collision ionization requiring absorption area, transition area, and multiplication area. Therefore, achievement of the avalanche effect in the MgZnO-based MSM PDs still faces many difficulties and challenges. The only MgZnO-based avalanche photodetector (APD) with MSM structure was achieved using MgO as the multiplication area. [8] Herein, MgZnO/Au/ZnO sandwich structure PD (SSPD) based on MSM structure was proposed. Using the particularity of the sandwich structure, the avalanche effect was successfully achieved, while simultaneously improving the EQE of the PD. High EQE of the SSPD comes from the interface defect between ZnO and MgZnO. The existence of defects destroys the periodic potential field generated by the atoms strictly arranged periodically; thus, the energy level that allows electrons to be introduced into the forbidden band of semiconductor is formed. These defect energy levels freely exchange electrons with the conduction band to act as traps. [15] These traps then produce the photoconductive (PC) gain, which is attributed to the capture of holes by the traps at the interface in SSPD. [16] The avalanche effect of SSPD originates from the collision ionization process that occurs inside the MgZnO film. SSPD forms a channel owing to the contact between ZnO and MgZnO. The channel in the MgZnO layer is far away from the defect concentration, which provides a powerful condition for collision ionization. Sandwich structure easily achieves the avalanche effect compared to MSM structure.In this study, MgZnO/Au/ZnO SSPD with a low dark current was successfully fabricated. Under the 275 nm

Improved Self-Powered Photodetection of Ferroelectric PbZr0.52Ti0.48O3 Thin Films via Interfacial Engineering

“…Preliminary analysis suggests that the external quantum efficiencies (EQEs) of both PDs exceeds 100%, which may be attributed to the strong depolarization electric field within the ferroelectric PZT thin film. Briefly, the strong depolarization electric field effectively separates the photogenerated charge carriers, and it may further produce additional charge carriers simultaneously via the typical impact ionization process. − However, the mechanisms of such interesting results need to be explored in depth in the future. It is worth noting that the photodetection performances of our PDs are better than related works reported before (Table ), which can be attributed to the high optical transparency of the top Au electrode, efficient optical absorption, and improved ferroelectric properties of the PZT thin film.…”

Formation of Micro‐Patterned Ga2O3/Se Heterojunction and its Application to Highly Sensitive Avalanche Photodiode

“…Previously, several studies have reported APD with EQE higher than 100% for UV detection. [ 37,39,40 ]…”

“…The free carriers that pass through the Ga 2 O 3 /Se heterojunction would begin accelerating to high energy and generate more charge carriers by ionization collision. [18,[35][36][37] The electric field in the c-Se layer is calculated to be %1 Â 10 5 V cm À1 . This current increase is considered to be the onset of avalanche behavior.…”

“…Previously, several studies have reported APD with EQE higher than 100% for UV detection. [37,39,40] It can be considered that EQE increased with the decreasing active area owing to the micro-scaling effect. The miniaturization of photodiodes increases the surface-to-volume ratio, which decreases the volume-dependent heat capacity.…”

Use of Organic Polymer P3HT:PC61BM as the Active Layer to Improve the Performance of ZnO Ultraviolet Photodetector

“…Because of the improvement of social needs and people’s lives, UV PDs have become important devices for human activities. − UV PDs have been widely used in military fields and commercial, such as gas sensing, missile detection, flame sensing, UV guidance, fire detection, environmental monitoring, medical applications, and optical communications . The band gap of ZnO is 3.37 eV, and the corresponding absorption wavelength is in the UV band. , Therefore, it shows that ZnO is an exceedingly good UV PD material.…”