MXene-GaN van der Waals metal-semiconductor junctions for high performance multiple quantum well photodetectors

A MXene-GaN-MXene based multiple quantum well photodetector was prepared on patterned sapphire substrate by facile drop casting. The use of MXene electrodes improves the responsivity and reduces dark current, compared with traditional Metal-Semiconductor-Metal (MSM) photodetectors using Cr/Au electrodes. Dark current of the device using MXene-GaN van der Waals junctions is reduced by three orders of magnitude and its noise spectral intensity shows distinct improvement compared with the traditional Cr/Au–GaN–Cr/Au MSM photodetector. The improved device performance is attributed to low-defect MXene-GaN van der Waals interfaces. Thanks to the high quality MXene-GaN interfaces, it is possible to verify that the patterned substrate can locally improve both light extraction and photocurrent collection. The measured responsivity and specific detectivity reach as high as 64.6 A/W and 1.93 × 1012 Jones, respectively, making it a potential candidate for underwater optical detection and communication. The simple fabrication of MXene-GaN-MXene photodetectors spearheaded the way to high performance photodetection by combining the advantages of emerging 2D MXene materials with the conventional III-V materials.

The Effects of Temperature on the Growth of a Lead-Free Perovskite-Like (CH3NH3)3Sb2Br9 Single Crystal for An MSM Photodetector Application

We have fabricated a photodetector based on (CH3NH3)3Sb2Br9 (MA3Sb2Br9) lead-free perovskite-like single crystal, which plays an important role in the optoelectronic characteristics of the photodetector as a perovskite-like photosensitive layer. Here, MA3Sb2Br9 single crystals were synthesized by an inverse temperature crystallization process with a precursor solution at three different growth temperatures, 60 °C, 80 °C, and 100 °C. As a result, a MA3Sb2Br9 single crystal with an optimum growth temperature of 60 °C presented a low trap density of 2.63 × 1011 cm−3, a high charge carrier mobility of 0.75 cm2 V−1 s−1, and excellent crystal structure and optical absorption properties. This MA3Sb2Br9 perovskite-like photodetector displayed a low dark current of 8.09 × 10−9 A, high responsivity of 0.113 A W−1, and high detectivity of 4.32 × 1011 Jones.

Design of Laser Ranging Device Using the Improved Photodetector and Its Usage in Geosynchronous Earth Orbit Navigation Satellite Orbit Determination

The geosynchronous earth orbit (GEO) satellites have good coverage performance and are widely used in WAAS, BDS, CAPS and other regional augmentation and regional navigation systems. At the same time, the precise orbit determination and prediction of such satellites play a significant role in high-precision navigation and user real-time positioning. In order to obtain higher accuracy of orbit determination, the laser ranging device is improved by equipping with a silicon-substrate germanium MSM photodetector in this study. In addition, the surface plasmon resonance augmentation effect is further studied to further enhance the photoelectric performance of the silicon-substrate germanium MSM photodetector. The detector is connected to the OPA657. The corresponding pre-amplified circuit is further designed in this study so that the laser ranging device can be used for the orbit determination application of GEO navigation satellites. In the experiment, the designed silicon-substrate germanium MSM photodetector is tested firstly, the finite-different time-domain (FDTD) method is used to analyze the structure of the photodetector. Then, the effects of the structural parameters such as the grating period on the resonance augmentation of the designed photodetector are analyzed. The results reveal that the photodetector has the best performance at 1500 nm with the absorption enhancement factor of higher than 7. The GNSS combined with the laser ranging is used for comparing the orbit determination errors of GEO satellites. 10 laser observation stations are selected, some of which are equipped with the laser ranging device designed in this study and supply to various GEO satellites for information collection. The results show that GEO satellites have to be introduced to the system deviation when adding the laser ranging data, otherwise they will deviate from the orbit. In addition, the laser ranging device designed in this study can significantly reduce the deviation caused by the introduction of laser ranging data from GEO satellites compared with traditional laser ranging devices.

Self-driven WSe2 photodetectors enabled with asymmetrical van der Waals contact interfaces

Self-driven photodetectors that can detect light without any external voltage bias are important for low-power applications, including future internet of things, wearable electronics, and flexible electronics. While two-dimensional (2D) materials exhibit good optoelectronic properties, the extraordinary properties have not been fully exploited to realize high-performance self-driven photodetectors. In this paper, a metal–semiconductor–metal (MSM) photodetector with graphene and Au as the two contacts have been proposed to realize the self-driven photodetector. Van der Waals contacts are formed by dry-transfer methods, which is important in constructing the asymmetrical MSM photodetector to avoid the Fermi-level pinning effect. By choosing graphene and Au as the two contact electrodes, a pronounced photovoltaic effect is obtained. Without any external bias, the self-driven photodetector exhibits a high responsivity of 7.55 A W−1 and an ultrahigh photocurrent-to-dark current ratio of ~108. The photodetector also shows gate-tunable characteristics due to the field-induced Fermi-level shift in the constituent 2D materials. What is more, the high linearity of the photodetector over almost 60 dB suggests the easy integration with processing circuits for practical applications.