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Using picosecond Raman scattering, hot-phonon occupation numbers (N) of GaAs and GaAs-like LO phonons have been studied over a wide range of structural parameters in more than 30 GaAs/Al Gal As superlattices. In addition, simultaneous measurements of these LO phonon modes in bulk GaAs and Al Gal "As alloys are made for comparison. N values of both GaAs and GaAs-like modes of the superlattices are comparable to or larger than those of bulk GaAs or Al Gal As alloys for x &0.2. On the other hand, N values of GaAs or GaAs-like LO phonons are much smaller for 0

Layered transition metals dichalcogenides such as MoS2 and WS2 have shown a tunable bandgap, making them highly desirable for optoelectronic applications. Here, we report on one-step chemical vapor deposited MoS2, WS2 and MoxW1-xS2 heterostructures incorporated into photoconductive devices to be examined and compared in view of their use as potential photodetectors. Vertically aligned MoS2 nanosheets and horizontally stacked WS2 layers, and their heterostructure form MoxW1-xS2, exhibit direct and indirect bandgap, respectively. To analyze these structures, various characterization methods were used to elucidate their properties including Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and high-resolution transmission electron microscopy. While all the investigated samples show a photoresponse in a broad wavelength range between 400 nm and 700 nm, the vertical MoS2 nanosheets sample exhibits the highest performances at a low bias voltage of 5 V. Our findings demonstrate a responsivity and a specific detectivity of 47.4 mA W−1 and 1.4 × 1011 Jones, respectively, achieved by MoxW1-xS2. This study offers insights into the use of a facile elaboration technique for tuning the performance of MoxW1-xS2 heterostructure-based photodetectors.