A chemically treated IGZO-based highly visible-blind UV phototransistor with suppression of the persistent photoconductivity effect

Abstract

In the past few years, there has been growing interest in ultraviolet (UV) photodetectors for various applications. A key requirement for UV photodetectors is the ability to exclusively detect light in the pure UV range while blocking visible light and avoiding interference from adjacent wavelengths. In this study, an indium–gallium–zinc-oxide (IGZO) thin-film transistor (TFT) was developed as a visible-blind UV phototransistor. To achieve this, chemical engineering was employed using ethylene glycol (EG) and 2-ethoxyethanol (2-EE) in the IGZO active layer. This resulted in a reduction of impurities that could act as subgap states in the thin film and an increase in the presence of hydroxide (OH⁻) bonds on the surface, effectively suppressing the R/G/B photoresponse induced by trap sites. Simultaneously, the photoresponse under UV illumination was enhanced, leading to a high photosensitivity value of 3.12 × 10⁷. Furthermore, additional ultraviolet ozone (UVO) treatment was performed to further modify the chemical composition. This treatment reduced the light response associated with traps, resulting in clearer detection of blue light near the UV range. The highest photosensitivity of blue light strikingly decreased from 2.30 × 10⁶ to 3.68 × 10⁵ with a UVO duration of 3 min. In particular, the UVO-treated sample exhibited a substantial and dramatic decrease in blue photoresponsivity from 2.1 × 10⁵ to a mere 3.3 at gate bias (V_G) = −10 V. It also had a positive impact on the light modulation properties, reducing the recovery time after light exposure and minimizing the persistent photoconductive (PPC) effect. These promising results pave the way for the utilization of 2-EE, EG incorporated-IGZO (2EEG-IGZO) phototransistors with high selectivity in the pure UV region across a wide range of applications, including space communication and environmental monitoring systems.