Low-noise, high-detectivity, polarization-sensitive, room-temperature infrared photodetectors based on Ge quantum dot-decorated Si-on-insulator nanowire field-effect transistors

Low-Dimensional-Materials-Based Photodetectors for Next-Generation Polarized Detection and Imaging

The vector characteristics of light and the vectorial transformations during its transmission lay a foundation for polarized photodetection of objects, which broadens the applications of related detectors in complex environments. With the breakthrough of low-dimensional materials (LDMs) in optics and electronics over the past few years, the combination of these novel LDMs and traditional working modes is expected to bring new development opportunities in this field. Here, the state-of-the-art progress of LDMs, as polarization-sensitive components in polarized photodetection and even the imaging, is the main focus, with emphasis on the relationship between traditional working principle of polarized photodetectors (PPs) and photoresponse mechanisms of LDMs. Particularly, from the view of constitutive equations, the existing works are reorganized, reclassified, and reviewed. Perspectives on the opportunities and challenges are also discussed. It is hoped that this work can provide a more general overview in the use of LDMs in this field, sorting out the way of related devices for "more than Moore" or even the "beyond Moore" research.

Large-Area GeSe Realized Using Pulsed Laser Deposition for Ultralow-Noise and Ultrafast Broadband Phototransistors

Here, we report on the comprehensive growth, characterization, and optoelectronic application of large-area, two-dimensional germanium selenide (GeSe) layers prepared using the pulsed laser deposition (PLD) technique. Back-gated phototransistors based on few-layered 2D GeSe have been fabricated on a SiO₂/Si substrate for ultrafast, low noise, and broadband light detection, showing spectral functionalities over a broad wavelength range of 0.4-1.5 μm. The broadband detection capabilities of the device have been attributed to the self-assembled GeO_x/GeSe heterostructure and sub-bandgap absorption in GeSe. Besides a high photoresponsivity of 25 AW^-1, the GeSe phototransistor displayed a high external quantum efficiency of the order of 6.14 × 10³%, a maximum specific detectivity of 4.16 × 10¹⁰ Jones, and an ultralow noise equivalent power of 0.09 pW/Hz^1/2. The detector has an ultrafast response/recovery time of 3.2/14.9 μs and can show photoresponse up to a high cut-off frequency of 150 kHz. These promising device parameters exhibited by PLD-grown GeSe layers-based detectors make it a favorable choice against present-day mainstream van der Waals semiconductors with limited scalability and optoelectronic compatibility in the visible-to-infrared spectral range.

Interlayer Transition Induced Infrared Response in ReS2/2D Perovskite van der Waals Heterostructure Photodetector

The emerging Ruddlesden-Popper two-dimensional perovskite (2D PVK) has recently joined the family of 2D semiconductors as a potential competitor for building van der Waals (vdW) heterostructures in future optoelectronics. However, to date, most of the reported heterostructures based on 2D PVKs suffer from poor spectral response that is caused by intrinsic wide bandgap of constituting materials. Herein, a direct heterointerface bandgap (∼0.4 eV) between 2D PVK and ReS₂ is demonstrated. The strong interlayer coupling reduces the energy interval at the heterojunction region so that the heterostructure shows high sensitivity with the spectral response expanding to 2000 nm. The large type-II band offsets exceeding 1.1 eV ensure fast photogenerated carriers separation at the heterointerface. When this heterostructure is used as a self-driven photodetector, it exhibits a record high detectivity up to 1.8 × 10¹⁴ Jones, surpassing any reported 2D self-driven devices, and an impressive external quantum efficiency of 68%.

Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

Group IV nanocrystals (NCs), in particular from the Si–Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO₂ were obtained by magnetron sputtering deposition followed by rapid thermal annealing at 600 °C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, μ-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3–7 nm diameter) in a matrix of nanocrystallized HfO₂. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO₂ layers. Nanocrystallized HfO₂ with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO₂ and SiGe NCs–HfO₂ layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600–2000 nm at low temperatures. The high-quality SiGe NC/HfO₂ matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO₂ matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.

Photoluminescence properties of cuprous phosphide prepared through phosphating copper with a native oxide layer

Although cuprous phosphide (Cu₃P) has been widely studied and applied in other fields, its photoluminescence (PL) properties are rarely investigated. Herein, we report that Cu₃P can emit near-infrared light at 750 nm. We show that the annealing and the presence of cuprous oxide can enhance the PL emission. The mechanism of the PL enhancement is the improvement of crystal quality and the formation of a space charge region. Our results provide a reference for improving the PL properties of p-type semiconductors.