The fast development of the brain-inspired neuromorphic computing system has ignited an urgent demand for artificial synapses with low power consumption. In this work, it is the first time a light-stimulated low-power synaptic device based on a single GaN nanowire has been demonstrated successfully. In such an artificial synaptic device, the incident light, the electrodes, and the light-generated carriers play the roles of action potential, presynaptic/postsynaptic membrane, and neurotransmitter in a biological synapse, respectively. Compared to those of other synaptic devices based on GaN materials, the energy consumption of the single-GaN-nanowire synaptic device can be reduced by more than 92%, reaching only . It is proposed that the oxygen element can contribute to the synaptic characteristics by taking the place of the nitrogen site. Moreover, it is found that the dynamic “learning-forgetting” performance of the artificial synapse can resemble the behavior of the human brain, where less time is required to relearn the missing information previously memorized and the memories can be strengthened after relearning. Based on the experimental conductance for long-term potentiation (LTP) and long-term depression (LTD), the simulated network can achieve a high recognition rate up to 90% after only three training epochs. Such few training times can reduce the energy consumption in the supervised learning processes substantially. Therefore, this work paves an effective way for developing single-nanowire-based synapses in the fields of artificial intelligence systems and neuromorphic computing technology requiring low-power consumption.
2023, 11(10): 1667
Micro-nano optomechanical accelerometers are widely used in automobile, aerospace, and other industrial applications. Here, we fabricate mechanical sensing components based on an electrically pumped GaN light-emitting diode (LED) with a beam structure. The relationship between the blueshift of the electroluminescence (EL) spectra and the deformation of the GaN beam structure based on the quantum-confined Stark effect (QCSE) of the InGaN quantum well (QW) structure is studied by introducing an extra mass block. Under the equivalent acceleration condition, in addition to the elastic deformation of GaN-LED, a direct relationship exists between the LED’s spectral shift and the acceleration’s magnitude. The extra mass block (gravitational force: ) induced blueshift of the EL spectra is obtained and shows driven current dependency. A polymer sphere (PS; gravitational force: ) is placed at the center of the beam GaN-LED, and a blueshift of 0.061 nm is observed in the EL spectrum under the injection current of 0.5 mA. The maximum sensitivity of the acceleration is measured to be , and the maximum measurable acceleration is calculated to be . It indicates the simultaneous realization of high sensitivity and a broad acceleration measurement range. This work is significant for several applications, including light force measurement and inertial navigation systems with high integration ability.
2023, 11(9): 1583
Low-intensity light detection necessitates high-responsivity photodetectors. To achieve this, we report quantum well (InAs QW) photo-field-effect-transistors (photo-FETs) integrated on a Si substrate using direct wafer bonding. Structure of the InAs QW channel was carefully designed to achieve higher effective mobility and a narrower bandgap compared with a bulk , while suppressing the generation of defects due to lattice relaxations. High-performance 2.6 nm InAs QW photo-FETs were successfully demonstrated with a high on/off ratio of and a high effective mobility of . 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; 1.0–2.5 μm) near 2 μm thanks to bandgap engineering through InAs QW structures. Our result suggests that the InAs QW photo-FET is promising for high-responsivity and extended-range SWIR photodetector applications.
2023, 11(8): 1465
Heterojunction field-effect phototransistors using two-dimensional electron gas (2DEG) for carrier transport have great potential in photodetection owing to its large internal gain. A vital factor in this device architecture is the depletion and recovery of the 2DEG under darkness and illumination. This is usually achieved by adding an external gate, which not only increases the complexity of the fabrication and the electrical connection but also has difficulty ensuring low dark current (). Herein, a quasi-pseudomorphic AlGaN heterostructure is proposed to realize the self-depletion and photorecovery of the 2DEG, in which both the barrier and the channel layers are compressively strained, making the piezoelectric and spontaneous polarization reverse, thus depleting the 2DEG and tilting the entire barrier and channel band to form two built-in photogates. The fabricated solar-blind phototransistors exhibit a very low below , a superhigh responsivity () of , a record high detectivity () of Jones, and an ultrafast response speed at the nanosecond level. The high performance is attributed to the efficient depletion and recovery of the full 2DEG channel by the two photogates, enabling direct detection of the sub-fW signal. This work provides a simple, effective, and easily integrated architecture for carrier control and supersensitive photodetection based on polarization semiconductors.
2023, 11(7): 1217
Photoelectric logic gates (PELGs) are the key component in integrated electronics due to their abilities of signal conversion and logic operations. However, traditional PELGs with fixed architectures can realize only very limited logic functions with relatively low on–off ratios. We present a self-driving polarized photodetector driven by the Dember effect, which yields ambipolar photocurrents through photonic modulation by a nested grating. The ambipolar response is realized by exciting the whispering-gallery mode and localized surface plasmon resonances, which leads to reverse spatial carrier generation and therefore the contrary photocurrent assisted by the Dember effect. We further design a full-functional PELG, which enables all five basic logic functions (“AND”, “OR”, “NOT”, “NAND”, and “NOR”) simultaneously in a single device by using one source and one photodetector only. Such an all-in-one PELG exhibits a strong robustness against structure size, incident wavelength, light power, and half-wave plate modulation, paving a way to the realization of ultracompact high-performance PELGs.
2023, 11(7): 1148
We developed a hybrid structure photodetector combining one-dimensional (1D) inorganic GaAs nanowires and two-dimensional (2D) organic perovskite materials, which can achieve various performance enhancements using a relatively simple structure. Via the optical absorption enhancement of perovskite and the type-II energy band structure formed by the heterostructure, the responsivity and detectivity of the photodetector from ultraviolet (UV) to visible (Vis) wavelengths are significantly enhanced, reaching 75 A/W and Jones, respectively. The response time of the photodetector was significantly decreased by 3 orders, from 785 ms to 0.5 ms, and the dark current was further reduced to 237 fA. A photodetector was prepared with enhanced responsivity and ultrafast response time in the multiband region from the UV to Vis wavelength. To the best of our knowledge, this is the first time to combine inorganic III-V GaAs nanomaterials with organic perovskite materials, which verifies the effective combination of inorganic and organic materials in a mixed dimension. The excellent photoelectric performance of the perovskite/GaAs-nanowire hybrid structure photodetector makes it a potential candidate material for a wide range of photoelectric applications such as multiband photodetection.
2023, 11(4): 541
The absence of efficient red-emitting micrometer-scale light emitting diodes (LEDs), i.e., LEDs with lateral dimensions of 1 μm or less is a major barrier to the adoption of microLEDs in virtual/augmented reality. The underlying challenges include the presence of extensive defects and dislocations for indium-rich InGaN quantum wells, strain-induced quantum-confined Stark effect, and etch-induced surface damage during the fabrication of quantum well microLEDs. Here, we demonstrate a new approach to achieve strong red emission () from dislocation-free N-polar InGaN/GaN nanowires that included an InGaN/GaN short-period superlattice underneath the active region to relax strain and incorporate more indium within the InGaN dot active region. The resulting submicrometer-scale devices show red electroluminescence dominantly from an InGaN dot active region at low-to-moderate injection currents. A peak external quantum efficiency and a wall-plug efficiency of 2.2% and 1.7% were measured, respectively, which, to the best of our knowledge, are the highest values reported for a submicrometer-scale red LED. This study offers a new path to overcome the efficiency bottleneck of red-emitting microLEDs for a broad range of applications including mobile displays, wearable electronics, biomedical sensing, ultrahigh speed optical interconnect, and virtual/augmented reality.
2022, 10(12): 2809
In this work, high-stability 4H-SiC avalanche photodiodes (APDs) for ultraviolet (UV) detection at high temperatures are fabricated and investigated. With the temperature increasing from room temperature to 150°C, a very small temperature coefficient of 7.4 mV/°C is achieved for the avalanche breakdown voltage of devices. For the first time, the stability of 4H-SiC APDs is verified based on an accelerated aging test with harsh stress conditions. Three different stress conditions are selected with the temperatures and reverse currents of 175°C/100 µA, 200°C/100 µA, and 200°C/500 µA, respectively. The results show that our 4H-SiC APD exhibits robust high-temperature performance and can even endure more than 120 hours at the harsh aging condition of 200°C/500 µA, which indicates that 4H-SiC APDs are very stable and reliable for applications at high temperatures.silicon carbide photodiode UV detector high temperature avalanche Geiger mode
Chinese Optics Letters
2023, 21(3): 032502
Solution process is a key technique for the manufacture of large-area and low-cost semiconducting devices and, thus, attracts a lot of attention from both academia and industry. Herein, we realized solution-processed light-emitting diodes (excluding a cathode) based on aggregation-induced emission (AIE) molecules of tetraphenylethylene-4Cl (TPE-4Cl) and cadimum-free semiconductor nanocrystals (NCs) for the first time. By mixing Cu-In-Zn-S NCs and TPE-4Cl as an emissive layer, a new type of environmentally friendly white-light-emitting diodes (WLEDs) was prepared through a solution-processed technique. After systematical optimization of the as-prepared WLEDs, the corresponding color rendering index can reach up to 87 with a maximum luminance of . This study may pave a new road to realize AIE-based WLEDs through a solution-processed technique.
2022, 10(11): 2622