Quantum Dot–Carbon Nanotube Hybrid Phototransistor with an Enhanced Optical Stark Effect

Abstract

Enhanced carrier–carrier interactions in hybrid nanostructures exhibit exceptional electronic and optoelectronic properties. Carbon nanotubes demonstrate excellent switching behavior with high on/off ratio and high mobility but do not show photoresponse in the visible range, whereas quantum dots (QDs) shows excellent optical response in various optical ranges which can be tuned with diameter. Here, a simple and effective way to develop hybrid phototransistors with extraordinary optoelectronic properties is presented by decorating semiconducting QDs on the surface of a single‐walled carbon nanotube (SWCNT). This hybrid structure demonstrates clear negative photoresponse and optical switching behavior, which could be further tuned by applying external gate bias in the future. A clear type conversion of SWCNT transistor from p‐type to n‐type caused by a charge transfer from attached QDs to CNT is demonstrated. Moreover, this hybrid structure also demonstrates an enhancement in ‘optical Stark effect’ without applying any external electric field. Charged SWCNT surface plays a key role behind the enhancement of optical Stark effect in QDs. The carrier dynamics of the QD and CNT heterostructures system highlights the potential application opportunity of the quantum dot systems, which can be adaptable to the current technologies.

Boosting photoresponse in silicon metal-semiconductor-metal photodetector using semiconducting quantum dots

“…The discrete energy levels of quantum dots (confined in low dimension) and their transition energy shift due to the Stark effect under external electric field were observed previously, causing these PL peak shifts1416. An asymmetric change of electron and hole wave functions and the electron-hole overlap integral under an external electric field in a quantum confined structure result in Stark effect1416. These results highlight that the radiative recombination transition energies (PL peak shift) in QDs can be tuned by applied substrate potentials.…”

“…This leads to numerous exotic electronic and optoelectronic properties in QDs, significantly different from their bulk states12131415. Exciton (or carrier) multiplication13, Stark effect14, and band shifting15 are among the key optoelectronic properties of semiconducting QDs that could be exploited to improve MSM photodetector operations. Therefore, a highly efficient and monolithic MSM photodetector device can be designed by incorporating semiconducting QDs in Si-based MSM device structure (Si-QD).…”

Uncooled Carbon Nanotube Photodetectors

“…A related approach was recently demonstrated using layers of C 60 deposited on CNT thin film transistors [39] with a detectivity of 10 9 cm Hz 1/2 /W in the near-IR. Quantum dots [40] with absorption in the visible have also been used in the same spirit.…”

Utilizing Electrical Characteristics of Individual Nanotube Devices to Study the Charge Transfer between CdSe Quantum Dots and Double-Walled Nanotubes

“…Both the DWNT−QD systems and pristine DWNTs exhibit similar ambipolar characteristics with similar "on current" levels, indicating that the chemical process involved in the QD decoration did not impact the electronic transport through the DWNT, likely because only the outer shell is affected by the functionalization process. This finding stands in stark contrast with other publications, 16,18,19 wherein, after QD decoration, these devices consisting exclusively of SWNT networks showed a large current decrease, an observation thereby further confirming the validity, significance, and novelty of our using DWNTs in this study. When averaging V min for all devices created both with and without functionalization, a negative shift of V min is observed consistently between the functionalized and pristine DWNTs, as shown in Figure 3A.…”