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The development of new technology, which would be able to shift photosensitivity of Si devices to the mid-infrared range, preserving the benefits of cheap silicon readout circuits, is of high priority for short-wave infrared photo-detection in defense, medical, night vision, and material production applications. Group IV GeSn-based materials have recently shown promising optoelectronic characteristics, allowing extension of the detection range to the mid-infrared region. However, the electronic properties of the material are not well understood and need further research. In this work, we provide temperature dependent studies of carrier lifetime, diffusion coefficient, and diffusion length in Ge0.95Sn0.05 epilayer on silicon by applying contactless light induced transient grating technique. The observed temperature dependence of lifetime was explained by the recombination of carriers on vacancy-related defects. The electron and hole capture cross sections were calculated. The temperature dependence of the diffusion coefficient indicated hole mobility limited by phonon and defect scattering. Weakly temperature dependent diffusion length of ∼0.5 μm verified material suitability for efficient submicrometer-thick optoelectronic devices. [ABSTRACT FROM AUTHOR]

Quasi-two dimensional perovskites demonstrate unique excitonic properties due to their multilayer structure making them attractive for various optoelectronic applications. However, the thickness of individual perovskite sheets in wet cast quasi-2D layers tends to randomly fluctuate giving rise to a specific type of disorder, which impacts on the carrier dynamics and is rather complex and remains understudied. Here, we present a study of carrier transport in Ruddlesden–Popper type (PEA)2FAn−1PbnBr3n+1 layers of order n from one to four, and in the bulk FAPbBr3 layer. We use a light induced transient grating technique to measure the carrier diffusion coefficient directly, and the transient absorption via photoluminescence to investigate the energy relaxation pathways. We observe two distinct energy transfer processes on different time scales. Fast energy funnelling in thicker (n ≥ 3) layers is observed up to 10 ps after excitation; we attribute this to short-distance transfer of excitons to neighbouring perovskite sheets of higher order. On the longer timescale of hundreds of picoseconds, carrier in-plane transport is governed by exciton diffusion in n = 1 and 2 layers and by free carrier plasma in thicker ones. Within the carrier density range of (0.5–4) × 1019 cm−3, the exciton diffusion coefficient in n = 1, 2 increases slowly from 1 to 2.8 cm2 s−1, whereas in thicker layers the dependence is much stronger and the diffusivity grows from 0.09 to 1.9 cm2 s−1. We explain these dependencies by a higher structural order in the thinner samples and the stronger localization of carriers in thicker ones. Also, amplified spontaneous emission (ASE) is observed in thicker (n ≥ 3) layers in electron–hole plasma, as evidenced by the typical ASE line redshift upon excitation. [ABSTRACT FROM AUTHOR]