Two-Photon Absorption Induced Photocurrent of a ß-Ga₂O₃ Film Photodetector

The ultra-wide bandgap and diverse material systems of gallium oxide (Ga2O3) make it an attractive candidate for cutting-edge semiconductor research. In this work, two-photon absorption induced photocurrent generation in a β-Ga2O3 film photodetector was investigated using femtosecond laser pulses over a wide range of average incident powers and input laser wavelengths. The occurrence of two-photon absorption (TPA) in nonlinear photocurrent generation was confirmed by analyzing the power-dependent response in which the photocurrent of the β-Ga2O3 film photodetectors shows a quadratic dependence on incident power. The spectral response of the TPA photocurrent peaks around 200 nm, exhibiting a 50 nm blue shift compared to the one-photon response. This difference results from their distinct selection rules. The large blue shift into the ultraviolet (UV) spectral region is advantageous for measuring the pulse duration of ultrafast laser pulses in the UV region. Subsequently, we tentatively performed an autocorrelation measurement based on the TPA-induced photocurrent of the β-Ga2O3 film photodetectors at 400 nm. This approach shows potential for developing an autocorrelator to measure ultrafast laser pulses in the ultraviolet region of 370 to 440 nm, as indicated by the TPA photocurrent spectrum.