Photovoltaic and flexible deep ultraviolet wavelength detector based on novel β-Ga2O3/muscovite heteroepitaxy

Abstract

Flexible and self-powered deep ultraviolet (UV) photodetectors are pivotal for next-generation electronic skins to enrich human life quality. The fabrication of epitaxial β-Ga2O3 thin films is challenging on flexible substrates due to high-temperature growth requirements. Herein, β-Ga2O3 ($$\stackrel{-}{2}$$ 2 - 0 1) films are hetero-epitaxially grown on ultra-thin and environment-friendly muscovite mica which is the first time β-Ga2O3 epitaxy growth on any flexible substrate. Integration of Gallium oxide with muscovite enables high-temperature processing as well as excellent flexibility compared to polymer substrates. Additionally, the metal–semiconductor-metal (MSM) photodetector on β-Ga2O3 layer shows an ultra-low dark current of 800 fA at zero bias. The photovoltaic peak responsivity of 11.6 µA/W is obtained corresponding to very weak illumination of 75 μW/cm2 of 265 nm wavelength. Thermally stimulated current (TSC) measurements are employed to investigate the optically active trap states. Among these traps, trap with an activation energy of 166 meV dominates the persistence photocurrent in the devices. Finally, photovoltaic detectors have shown excellent photocurrent stability under bending induced stress up to 0.32%. Hence, this novel heteroepitaxy opens the new way for flexible deep UV photodetectors.

Deep-Level Traps Responsible for Persistent Photocurrent in Pulsed-Laser-Deposited β-Ga2O3 Thin Films

“…The photocurrent was observed to last for several seconds. Such a curve follows a biexponential equation [26,27]:…”

Flexible strategy of epitaxial oxide thin films

“…Overall, the flexible PZT film on mica exhibits high epitaxial quality and excellent ferroelectricity, which can be tuned by mechanical strain. Besides, other oxides have also been demonstrated, including transparent conducting oxides Al-ZnO (AZO) and ITO ( Bitla et al., 2016 ), magnetic CFO ( Liu et al., 2017a , 2017b ), BaFe 12 O 19 ( Ke et al., 2021 ) and Fe 3 O 4 ( Zheng et al., 2018 ), antiferroelectric PbHfO 3 (PHO) ( Tsai et al., 2021 ) and PbZrO 3 (PZO) ( Ko et al., 2021 ), wide bandgap semiconductor Ga 2 O 3 ( Tak et al., 2020 ), conducting SRO ( Liu et al., 2018 ), ferroelectric Pr-doped Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCTZ:Pr) ( Zheng et al., 2019a ), BiFeO 3 (BFO) ( Sun et al., 2020a , 2020b ) and PZT ( Jiang et al., 2017 ), colossal magnetoresistance Pr 0.5 Ca 0.5 MnO 3 (PCMO) ( Yen et al., 2020 ), phase transition VO 2 ( Li et al., 2016 ), etc.

Figure 3 Direct growth of oxide thin films on flexible mica (A) Standard θ-2θ XRD scan of the heterostructure; (B) φ-scans at PZT{002}, SRO{002}, CFO{004}, and mica{202} diffraction peaks; (C) The reciprocal space mapping of the heterostructure; (D) The cross-sectional TEM image showing the PZT/SRO and SRO/CFO/mica interfaces along with the selected area diffraction patterns of PZT, SRO, and mica; (E) Representative local PFM amplitude and phase hysteresis loops; (F) The local coercive voltage variation as a function of bending radius ( Jiang et al., 2017 ).

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A Comprehensive Review on Recent Developments in Ohmic and Schottky Contacts on Ga2O3 for Device Applications

“…β-Ga 2 O 3 has a high breakdown electric field strength of 8 MV/cm and exceptional Baliga figure of merit (BFOM) and Johnson’s figure of merit (JFOM) due to ultrawide bandgap of 4.6–4.9 eV, much higher than those of SiC and GaN. β-Ga 2 O 3 has a high saturation electron velocity ( v s ) of 2 × 10 7 cm/s, which allows for high current density and high-frequency operation. ,− …”