The effect of thickness and/or doping on the nonlinear and saturable absorption behaviors in amorphous GaSe thin films

Abstract

Articles you may be interested inImpacts of Si-doping and resultant cation vacancy formation on the luminescence dynamics for the near-bandedge emission of Al0.6Ga0.4N films grown on AlN templates by metalorganic vapor phase epitaxyWe investigated the nonlinear and saturable absorption characteristics of very thin amorphous undoped GaSe, Ge ͑0.01 at. %͒, and Sn ͑0.5 at. %͒ doped GaSe films by pump-probe and open aperture Z-scan techniques. Linear absorption measurements indicate blueshift in energy with increasing film thickness. Thinner films exhibit saturable absorption while thicker films exhibit nonlinear absorption for 4 ns and 65 ps pulse durations. The films exhibit competing effects between nonlinear and saturable absorption. Saturable absorption behavior weakens while nonlinear absorption appears with increasing film thickness. In addition to that, saturable absorption behavior is very sensitive to doping. Doping causes absorption behaviors to appear in thinner films compared to undoped films. These behaviors are attributed to increasing localized defect states with increasing film thickness and doping. To derive the transmission in open aperture Z-scan data, a theoretical model incorporating one photon, two photon, and free carrier absorptions and their saturations were considered. The experimental curves were fitted to the theory of open aperture Gaussian beam Z-scan based on the Adomian decomposition method. Nonlinear absorption coefficients and saturation intensity thresholds were extracted from the fitting of the experimental results for both pulse durations used for the experiments. Saturation intensity threshold values increased with increasing film thickness and doping. The lowest saturation intensity threshold for undoped GaSe film was found to be 1.9ϫ 10 −3 GW/ cm 2 for 45 nm film thickness and increased about two orders of magnitude for 74 nm film thickness.

The effect of thickness and doping on the nonlinear absorption behaviour of IIIA-VIA group amorphous semiconductor thin films

“…Nonlinear absorption in semiconductors with thickness values in the range of microns is extensively studied in the literature [9,10]. Recently in our studies, we show that decreasing thickness as well as dopant ratio results in decreasing I sat and increasing thickness and dopant ratio results in increasing β eff value for InSe and GaSe amorphous thin films [11,12].…”

Ultrafast Nonlinear Optical Response and Carrier Dynamics in Layered Gallium Sulfide (GaS) Single-Crystalline Thin Films

“…The NLO parameters of multilayer β-GaS thin films and various metal monochalcogenide and 2D layered materials reported in recent literatures (Kürüm et al, 2010;Isik et al, 2013;Dong et al, 2016;Ren et al, 2016;Karatay, 2019;Ertap, 2018;Jia et al, 2020) are summarized in Table 1. Note that it should be cautious to compare the definite value of NLO coefficients measured at different wavelength and different pulse duration.…”

Structural and optical properties of gallium sulfide thin film

“…These values are less than the band gap values of bulk gallium sulfide crystal. This behavior is thought to be due to the blurring of the band gap by the defect states [25,26]. Steepness of the exponential absorption tail is determined from the absorption spectrum as:…”