Two -dimensional transition-metal dichalcogenides (2D-TMDs) have attracted attention for applications in electronics and photonics, as well as for the wealth of new scientific phenomena that arise at low dimensionality. Recently, the ability to grow 2D-TMDs by chemical vapor deposition has opened the path to large area devices, but also to the synthesis of semiconductor alloys with tunable bandgaps. In this presentation, I will discuss our recent experimental work in exploring the optoelectronic properties of 2D MoS_2(1-x)Se_2x alloys spanning the compositional range. In particular, we report the observation of a new regime of operation where the photocurrent depends superlinearly on light intensity. We use spatially-resolved photocurrent measurements on devices consisting of CVD-grown monolayers to show the photoconductive nature of the photoresponse, with the photocurrent dominated by recombination and field-induced carrier separation in the channel. Time-dependent photoconductivity measurements show the presence of persistent photoconductivity for the S-rich alloys, while photocurrent measurements at fixed wavelength for devices of different alloy compositions show a systematic decrease of the responsivity with increasing Se content associated with increased linearity of the current-voltage characteristics. A model based on the presence of different types of recombination centers is presented to explain the origin of the superlinear dependence on light intensity, which emerges when the non-equilibrium occupancy of initially empty fast recombination centers becomes comparable to that of slow recombination centers.
François Léonard, "Optoelectronics in two-dimensional semiconductor alloys (Presentation Recording)," Proc. SPIE 9553, Low-Dimensional Materials and Devices, 955310 (Presented at SPIE Nanoscience + Engineering: August 13, 2015; Published: 5 October 2015); https://doi.org/10.1117/12.2190303.4519371100001.
Conference Presentations are recordings of oral presentations given at SPIE conferences and published as part of the proceedings. They include the speaker's narration with video of the slides and animations. Most include full-text papers. Interactive, searchable transcripts and closed captioning are now available for most presentations.
Search our growing collection of more than 29,500 conference presentations, including many plenaries and keynotes.