Defect-driven photocarrier dynamics and thermal quenching of photocurrent in β-Ga2O3 thin films

Deciphering defect-governed photocarrier dynamics in ultrawide bandgap β-Ga 2 O 3 , is imperative for tailoring their functionalities in advanced optoelectronic architectures owing to its intrinsic ultraviolet transparency and high critical electric field. In this study, pulsed laser deposited β-Ga 2 O 3 thin films grown with various oxygen partial pressures (1 - 50 Pascal) leads to a modulation of the sub-band gap defects’ distribution. The films crystallized in the monoclinic β-Ga 2 O 3 phase show improvement in the crystal quality as the oxygen pressure increases. Room-temperature photoconductivity shows a photo-to-dark current ratio of ~4×10², responsivity of 50 mA/W, and fast rise-decay dynamics, making the films suitable for applications such as solar blind short-range secure space communications. The film deposited under lower oxygen pressure displays a sublinear power-law dependence, attributed to trap-assisted carrier dynamics and persistence of the photocarriers while the film grown at higher oxygen pressure shows an almost linear response, reflecting intrinsic band-to-band excitation with negligible defects’ role. The stable and repeatable photoresponse over multiple cycles confirms improved reliability and reproducibility of the films. The unprecedented temperature-dependent photocurrent measurements (12-300 K) reveal a rich variety of defect-dominated transport mechanisms operating across distinct temperature regimes. The analysis demonstrates a sequential transition from trap-mediated Efros-Shklovskii and Mott variable-range hopping (VRH), to nearest-neighbour hopping, and finally to thermally activated band conduction. Notably, each film exhibits these conduction processes over different characteristic temperature intervals, depending on the oxygen partial pressure used during growth. For the film deposited at 1 Pa (GO-1), VRH transport dominates below 50 K. In contrast, the film grown at 50 Pa (GO-50) retains VRH behaviour up to nearly 200 K. Additionally, thermal activation of recombination centres induces photocurrent quenching above ~100 K in GO-1 and above ~260 K in GO-40. These insights emphasize the fundamental significance of defect-carrier interactions in tailoring next-generation deep-UV and cryogenic optoelectronic devices. • β-Ga 2 O 3 films show photo-to-dark current ratio ~4×10 2 , 50 mA/W responsivity, and fast photocurrent rise–decay • ES-VRH to TABC transition via Mott VRH and NNH shifts to higher temperatures as oxygen rises. • Trap-rich and trap-suppressed films exhibit thermal quenching and continuous rise in photocurrent respectively