Fourier transform infrared ͑FTIR͒ spectrometer is a powerful tool for studying the photoluminescence ͑PL͒ properties of semiconductors, due to its well-known multiplexing and throughput advantages. However, it suffers from internal He-Ne laser disturbance in near-infrared and/or environmental background thermal emission in mid-and far-infrared spectral regions. In this work, a modulated PL technique is developed based on step-scan ͑SS͒-FTIR spectrometer. Theoretical analysis is conducted, and applications of the technique are given as examples in the PL study of mid-infrared HgCdTe thin films and near-infrared GaInP / AlGaInP multiple quantum wells, respectively. The results indicate that the He-Ne laser and/or thermal emission disturbance can be reduced at least 1 / 1000 and/or even 1 / 10 000, respectively, by the modulated SS-FTIR PL technique, and hence a rather smooth PL spectrum can be obtained even under room temperature for HgCdTe thin films. A brief comparison is given of this technique with previously reported phase-sensitive modulation methods based on conventional rapid-scan ͑RS͒-FTIR spectrometer, and the advantages of this technique over the former RS-FTIR-based ones are emphasized.
Although a lot of promising two-dimensional (2D) semiconductors with various bandgaps, represented by black phosphorus (0.3 eV), transition metal dichalcogenides (< 2 eV), and boron nitride (5 − 6 eV), have been extensively researched in photoelectronic and electronic devices, the spectrum of large bandgap materials is still very narrow, which limits the potential device applications in ultraviolet photodetection. The broad family of layered thio- and seleno-phosphates with wide and tunable bandgaps (1.3 − 3.5 eV) can complement the intermediate bandgaps from 1.6 to 4 eV, which can fill the gap between transition metal dichalcogenides and boron nitride. In this work, a high-performance ultraviolet photodetector based on multilayered CuInP2S6 was fabricated. It exhibits fast response times shorter than 0.5 ms, i.e., rise time ∼ 0.36 ms and fall time ∼ 0.44 ms for ultraviolet illumination (280 nm, 50 nW), which is superior than previously reported 2D layered-based UV detectors. Significantly, this photodetector also shows ultralow dark current (∼ 100 fA), a high on/off ratio (∼103), and a specific detectivity of 7.38 × 1010 Jones. Our results provide an excellent candidate for low power consumption and high-speed photodetection.
We report on a new technique of realizing photoreflectance (PR) spectroscopy with a step-scan Fourier-transform infrared spectrometer. The experimental configuration is briefly described and a detailed theoretical analysis is conducted. The results reveal two distinct features of this PR technique that (i) the PR related signal is enhanced by a factor of at least 100 relative to those of the conventional PR techniques and (ii) the unwanted spurious signal introduced by either diffuse reflected pump beam or pump-beam induced material's photoluminescence reaching the photodetector of the PR configuration is eliminated without any special consideration of normalization for deducing the final PR spectrum. Applications are given as examples in the study of GaNAs/GaAs single quantum wells and GaInP/AlGaInP multiple quantum wells, respectively, under different pump-beam excitation energy and/or power. The experimental results approve the theoretically predicted features and illustrate the possibility of investigating weak PR features by using high pump-beam power. A brief comparison of this technique with the conventional PR techniques is given, and the extendibility of this technique to long-wavelength spectral regions is pointed out.
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