Mixed-dimensional stacked nanocomposite structures for a specific wavelength-selectable ambipolar photoresponse

Mixed-dimensional composite structures using zero-dimensional(0D)quantum dots(QDs)and two-dimensional(2D)transition metal dichalcogenides(TMDs)materials are expected to attract great interest in optoelectronics due to the potential to generate new optical properties.Here,we report on the unique optical characteristics of a devices with mixed dimensional vertically stacked structures based on tungsten diselenide(WSe_(2))/CdSeS QDs monolayer/molybdenum disulfide(MoS_(2))(2D/0D/2D).Specifically,it exhibits an ambipolar photoresponse characteristic,with a negative photoresponse observed in the 400-600 nm wavelength range and a positive photoresponse appeared at 700 nm wavelength.It resulted in the high negative responsivity of up to 52.22 mA·W^(−1)under 400 nm,which is 163 times higher than that of the photodetector without CdSeS QDs.We also demonstrated the negative photoresponse,which could be due to increased carrier collision probability and non-radiative recombination.Device modeling and simulation reveal that Auger recombination among the types of non-radiative recombination is the main cause of negative photocurrent generation.Consequently,we discovered ambipolar photoresponse near a specific wavelength corresponding to the energy of quantum dots.Our study revealed interesting phenomenon in the mixed low-dimensional stacked structure and paved the way to exploit it for the development of innovative photodetection materials as well as for optoelectronic applications.

High-responsivity InAs quantum well photo-FET integrated on Si substrates for extended-range short-wave infrared photodetector applications

Low-intensity light detection necessitates high-responsivity photodetectors.To achieve this,we report In_(0.53)Ga_(0.47)As∕In As∕In_(0.53)Ga_(0.47)As quantum well(InAs QW)photo-field-effect-transistors(photo-FETs)integrated on a Si substrate using direct wafer bonding.Structure of the In As QW channel was carefully designed to achieve higher effective mobility and a narrower bandgap compared with a bulk In_(0.53)Ga_(0.47)As,while suppressing the generation of defects due to lattice relaxations.High-performance 2.6 nm In As QW photo-FETs were successfully demonstrated with a high on/off ratio of 10~5 and a high effective mobility of 2370 cm^(2)∕(V·s).The outstanding transport characteristics in the InAs QW channel result in an optical responsivity 1.8 times greater than InGaAs photo-FETs and the fast rising/falling times.Further,we experimentally confirmed that the InAs QW photo-FET can detect light in the short-wavelength infrared(SWIR;1.0–2.5μm)near 2μm thanks to bandgap engineering through In As QW structures.Our result suggests that the InAs QW photo-FET is promising for high-responsivity and extended-range SWIR photodetector applications.