Quasi-Epitaxial Growth of β-Ga 2 O 3 -Coated Wide Band Gap Semiconductor Tape for Flexible UV Photodetectors.

The epitaxial growth of technically important β-Ga 2 O 3 semiconductor thin films has not been realized on flexible substrates due to the limitations of high-temperature crystallization conditions and lattice-matching requirements. We demonstrate the epitaxial growth of β-Ga 2 O 3 (-201) thin films on flexible CeO 2 (001)-buffered Hastelloy tape. The results indicate that CeO 2 (001) has a small bi-axial lattice mismatch with β-Ga 2 O 3 (-201), inducing simultaneous double-domain epitaxial growth. Flexible photodetectors are fabricated on the epitaxial β-Ga 2 O 3 -coated tape. Measurements reveal that the photodetectors have a responsivity of 4 × 10 4 mA/W, with an on/off ratio reaching 1000 under 254 nm incident light and 5 V bias voltage. Such a photoelectrical performance is within the mainstream level of β-Ga 2 O 3 -based photodetectors using conventional rigid single-crystal substrates. More importantly, it remained robust against more than 20,000 bending test cycles. Moreover, the technique paves the way for the direct in situ epitaxial growth of other flexible oxide semiconductor devices in the future.