Voltage-Tunable UVC–UVB Dual-Band Metal–Semiconductor–Metal Photodetector Based on Ga2O3/MgZnO Heterostructure by RF Sputtering

Jie-Si Jheng,Chun-Kai Wang,Sheng-Po Chang,Shoou-Jinn Chang,Yu-Zung Chiou

doi:10.3390/coatings10100994

Jie-Si Jheng, Chun-Kai Wang + Show 3 more

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https://doi.org/10.3390/coatings10100994

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Abstract

Dual-band metal–semiconductor–metal (MSM) photodetectors (PDs) with a Ga2O3/MgZnO heterostructure were fabricated by radio frequency (RF) sputtering, which can detect ultraviolet C (UVC) and ultraviolet B (UVB) bands individually by controlling different bias voltages. A PD with the annealing temperature of Ga2O3 at 600 °C can improve the crystal quality of Ga2O3 thin film and exhibit the least persistent photoconductivity (PPC) effect. However, a PD with the annealing temperature of Ga2O3 at 600 °C cannot achieve a voltage-tunable dual-band characteristic. On the contrary, the PD without annealing can suppress the carriers from the bottom layer of MgZnO thin film at a lower bias voltage of 1 V. At this time, the peak responsivity at 250 nm was mainly dominated by the top layer of Ga2O3 thin film. Then, as the bias voltage increased to 5 V, the peak detection wavelength shifted from 250 (UVC) to 320 nm (UVB). In addition, the PD with a 25 nm–thick SiO2 layer inserted between Ga2O3 and MgZnO thin film can achieve a broader operating bias voltage range for dual-band applications.

Highlights

For solid-state lighting, ultraviolet (UV) light has unique applications compared with visible light
After the typical cleaning process, a 150 nm–thick MgZnO thin film was grown on the c-plane sapphire substrate, using an radio frequency (RF) magnetron sputter system (KD-SPUTTER, Kao Duen Technology Corp., New Taipei City, Taiwan)
External MSM PDs were fabricated by RF sputtering, and Responsivity these fabricated PDs could detect the UVCQuantum and ultraviolet B (UVB) dual-band individually by controlling different

Summary

Introduction

For solid-state lighting, ultraviolet (UV) light has unique applications compared with visible light. According to the different applications, UV light can be divided into three sub-bands: ultraviolet A (UVA) (320–400 nm), ultraviolet B (UVB) (280–320 nm), and ultraviolet C (UVC) (200–280 nm). Wide-bandgap semiconductor materials, such as Ga2 O3 , BeZnO, ZnO, Sr2 Nb3 O10 , Alx Ga1−x N, and Mgx Zn1−x O, have been generally used to design and fabricate UV photodetectors (PDs) [1,2,3,4,5,6,7,8,9,10,11]. Mgx Zn1−x O, a representative ternary alloy of wide-bandgap semiconductor material, has gained popularity for fabricating UVB and UVC optoelectronic devices due to its energy bandgap, ranging from 3.37 (ZnO) to 7.8 eV (MgO) [15,16,17,18].

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