Suppression of persistent photoconductivity in high gain Ga₂O₃ Schottky photodetectors*

Abstract

The defect-related photoconductivity gain and persistent photoconductivity (PPC) observed in Ga2O3 Schottky photodetectors lead to a contradiction between high responsivity and fast recovery speed. In this work, a metal–semiconductor–metal (MSM) Schottky photodetector, a unidirectional Schottky photodetector, and a photoconductor were constructed on Ga2O3 films. The MSM Schottky devices have high gain (> 13) and high responsivity (> 2.5 A/W) at 230–250 nm, as well as slow recovery speed caused by PPC. Interestingly, applying a positive pulse voltage to the reverse-biased Ga2O3/Au Schottky junction can effectively suppress the PPC in the photodetector, while maintaining high gain. The mechanisms of gain and PPC do not strictly follow the interface trap trapping holes or the self-trapped holes models, which is attributed to the correlation with ionized oxygen vacancies in the Schottky junction. The positive pulse voltage modulates the width of the Schottky junction to help quickly neutralize electrons and ionized oxygen vacancies. The realization of suppression PPC functions and the establishment of physical models will facilitate the realization of high responsivity and fast response Schottky devices.

Ultrasensitive Flexible κ-Phase Ga2O3 Solar-Blind Photodetector

“…For the log scale of the current spectrum shown in Figure c, a long tail can be observed after the peak response up to λ = 1100 nm, which could be attributed to the persistent photoconductivity (PPC) that commonly exists in Ga 2 O 3 PDs. − This PPC effect, which results from the oxygen vacancies-related traps, could reduce the PD response speed and increase the PD recovery time during the process of trapping and releasing photogenerated electrons in the trapping center. , For example, for a 1 V bias, the currents at λ = 250 and 1100 nm are about 4.3 × 10 –7 and 5.4 × 10 –14 A, respectively. The current at λ = 1100 nm is higher than the I dark (=4.4 × 10 –14 A) measured without illumination.…”

Directional Carrier Transport in Micrometer-Thick Gallium Oxide Films for High-Performance Deep-Ultraviolet Photodetection

“…In fact, very large inconsistency of the device parameters is seen in previous Ga 2 O 3 MSM photodetector studies, where the reported optimized t film values vary from 30 to 1000 nm. − While such inconsistency is likely attributed to different material qualities in these studies, it is not clear how the material defect affects the DUV photodetection behavior of a Ga 2 O 3 -based MSM photodetector and how to coordinate the device’s parameters for optimized performance. Particularly, a trade-off effect is commonly observed that relies on lattice defects as trap centers to enhance the photocurrent gain, which, however, inevitably compromises the response speed due to the slow detrapping process. − In this work, we perform a systematic study to understand how to design the device’s geometric parameters with Ga 2 O 3 characteristics and defects for fabricating high-performance MSM DUV photodetectors. It is discovered that adopting a micrometer thickness rather than a commonly suggested d p simultaneously achieves more than 18-fold enhancement of responsivity and over 100% enhancement of the response speed in ε-Ga 2 O 3 thin-film MSM photodetectors.…”

Electrical characteristics and photodetection mechanism of TiO2/AlGaN/GaN heterostructure-based ultraviolet detectors with a Schottky junction

“…Thirdly, even after the UV light is turned off, the trapping holes in the TiAu/AlGaN Schottky junction surface are still maintained due to the electric field, causing a persistent leakage current. 43–45…”

“…Thirdly, even after the UV light is turned off, the trapping holes in the TiAu/AlGaN Schottky junction surface are still maintained due to the electric field, causing a persistent leakage current. [43][44][45] Fig. 6(a)-(b) shows the curves of transient response photocurrent versus time for the Schottky junction-based TiO 2 / AlGaN/GaN heterostructure photodetector under 274 nm UV illumination with a light intensity of 504 mW cm À2 at negative bias V = À1.5 V and V = À4 V. The UV light was kept on and off for 50 s each.…”