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Pump–probe thermoreflectance has been commonly applied for characterizing the thermal properties of materials. Generally, a reliable and efficient non-linear fitting process is often implemented to extract unknown thermal parameters during the pump–probe thermoreflectance characterizations. However, when it comes to processing large amounts of data acquired from similar structural samples, non-linear fitting process appears to be very time-consuming and labor-intensive to search for the best fitting for every testing curve. Herein, we propose to apply deep learning (DL) approach to nanosecond transient thermoreflectance technique for high-throughput experimental data processing. We first investigated the effect of training set parameters (density and bounds) on the predictive performance of the DL model, providing a guidance to optimize the DL model. Then, the DL model is further verified in the measurement of the bulk sapphire, SiC, diamond samples, and GaN-based multilayer structures, demonstrating its capability of analyzing the results with high accuracy. Compared to the conventional non-linear fitting method (such as Global Optimization), the computation time of the new model is 1000 times lower. Such a data-driven DL model enables the faster inference and stronger fitting capabilities and is particularly efficient and effective in processing data acquired from wafer-level measurements with similar material structures. [ABSTRACT FROM AUTHOR]

Herein, a novel enhancement-mode (E-mode) GaN-based p-channel FETs (p-FETs) with a linearly graded AlGaN (LGA) p-channel is proposed and numerically studied by Silvaco TCAD. Thanks to strong polarization-induced doping, three-dimensional hole gas (3DHG) can be uniformly generated in LGA to form a continuous p-channel with a hole concentration over 1018 cm–3. Combined with an optimized recessed gate structure, the LGA p-FET can simultaneously achieve a large threshold voltage (| V TH|) > 2 V and a high current density (| J DS|) of ∼10 mA mm−1 at V DS = −10 V. Additionally, two critical parameters of the LGA p-FETs, i.e. the depth of recessed gate and initial Al composition of LGA, are specifically studied to reveal the unique carrier behavior of 3DHG in the devices. Importantly, the LGA structure is further optimized and implemented as the p-type cap layer to construct an E-mode GaN n-FET. Thereby, based on the same LGA configuration, a GaN-based inverter with the matched complementary n- and p-FETs is monolithically constructed, showing sharp voltage transition. The reported novel LGA structure and its availability in both GaN-based E-mode n- and p-FETs provides valuable insights and guidance to construct highly efficient GaN p-type devices and All-GaN-based integrated circuits for compact power electronic systems. [ABSTRACT FROM AUTHOR]

The p-GaN-gated E-mode HEMTs (P-HEMTs) are being extensively studied for emerging power electronics. However, the devices still suffer from performance trade-off among threshold voltage (V TH), output drain current (I DS), and breakdown voltage (V BD). Herein, we propose a P-HEMT with a stair-like p-GaN cap layer to boost their performance. The p-GaN cap layer is composed of four discrete p-GaN staircases with the decreased thickness to the right (R ight- S tair P -HEMT) or to the left (L eft- S tair P -HEMT). It is found that the RSP-HEMT simultaneously achieves the 1.3 times increased I DS, 160 V enhanced V BD, and improved V TH stability against drain-induced barrier lowering effects, compared with the LSP-HEMT and the conventional B a S eline P -HEMT. These device merits should be attributed to the effective manipulation of the lateral electric field (E F) under all bias conditions by the unique band structures enabled by the RSP configuration. Such E F manipulation strategies offer us helpful guidance and insights to further propel the development of high-performance E-mode P-HEMTs. [ABSTRACT FROM AUTHOR]

The development of artificial tetrachromatic vision holds great potential to enhance human color perception and discrimination, thereby enabling more effective navigation in diverse environments. Herein, an artificial tetrachromatic synaptic device is presented built upon 2D‐3D vertically stacked semiconductors composed of tungsten diselenide (WSe2)‐gallium nitride (GaN) configuration, forming a dual‐channel floating gate transistor (FGT). Under the concerted influence of electrical and optical stimulation, the device successfully mimics fundamental tetrachromatic synaptic behaviors, including short‐term potentiation (STP), weak long‐term potentiation (wLTP), long‐term potentiation (LTP), paired‐pulse facilitation (PPF), spike number‐dependent plasticity (SNDP), and spike rate‐dependent plasticity (SRDP). Notably, the plasticity of the device can be further modulated under ultraviolet (UV) stimulation, providing insights into the modulation of synaptic plasticity through the photogenerated carrier dynamics in the GaN channel. These results imply that WSe2‐GaN‐based FGT architecture with dual‐channel characteristics seamlessly integrates optical sensing and synaptic simulation functionalities, representing a promising avenue for the development of next‐generation artificial visual perception systems (AVPS), with a particular advantage for the pursuit of high‐performance artificial tetrachromatic neuromorphic computing applications of the future. [ABSTRACT FROM AUTHOR]

Light‐emitting diodes and photodiodes, often acting as transmitters and receivers, are two key optical components for constructing an optical communication system. Recently, solar‐blind optical wireless communication (SB‐OWC) has emerged as a promising free‐space communication platform due to its unique advantages, including low background noise, high security, and non‐line‐of‐sight ability. However, the development of deep ultraviolet (DUV) emitters and detectors is still in its early stages with relatively low efficiency and poor detection capability, which hampers the further progress of SB‐OWC. Herein, a triangular‐shaped micro‐sized diode (T‐μ‐diode) is reported that can significantly boost its DUV emission and detection performance compared with a regular circular‐shaped micro‐diode (C‐μ‐diode) due to improved current injection and enhanced light extraction/absorption behavior. Specifically, the T‐μ‐diodes demonstrate superior light output power with a −3 dB modulation bandwidth over 566 MHz operating at an extremely high current density of 2 kA cm−2 while possessing a higher photo‐responsivity of ≈160 mA W−1 with a faster response speed of 5.1 ns, surpassing the traditional C‐μ‐diodes in both light emitting and detecting modes. Importantly, a bidirectional on‐chip data transmission system is realized by simply switching the operation mode of two T‐μ‐diodes monolithically fabricated on the same platform with boosted emission and detection functionalities. [ABSTRACT FROM AUTHOR]