Photodetectors converting light signals into detectable photocurrents are ubiquitously in use today. To improve the compactness and performance of next-generation devices and systems, low dimensional materials provide rich physics to engineering the light–matter interaction. Photodetectors based on two-dimensional (2D) material van der Waals heterostructures have shown high responsivity and compact integration capability, mainly in the visible range due to their intrinsic bandgap. The spectral region of near-infrared (NIR) is technologically important, featuring many data communication and sensing applications. While some initial NIR 2D material-based detectors have emerged, demonstrations of doping-junction-based 2D material photodetectors with the capability to harness the charge-separation photovoltaic effect are yet outstanding. Here, we demonstrate a 2D p-n van der Waals heterojunction photodetector constructed by vertically stacking p-type and n-type indium selenide (InSe) flakes. This heterojunction charge-separation-based photodetector shows a threefold enhancement in responsivity in the NIR spectral region (980 nm) as compared to photoconductor detectors based on p- or n-only doped InSe. We show that this junction device exhibits self-powered photodetection operation, exhibits few pA-low dark currents, and is about 3–4 orders of magnitude more efficient than the state-of-the-art foundry-based devices. Such capability opens doors for low noise and low photon flux photodetectors that do not rely on external gain. We further demonstrate millisecond response rates in this sensitive zero-bias voltage regime. Such sensitive photodetection capability in the technologically relevant NIR wavelength region at low form factors holds promise for several applications including wearable biosensors, three-dimensional (3D) sensing, and remote gas sensing.

Van der Waals (vdWs) heterostructures, assembled by stacking of two-dimensional (2D) crystal layers, have emerged as a promising new material system for high-performance optoelectronic applications, such as thin film transistors, photodetectors, and light-emitters. In this study, we showcase an innovative device that leverages strain-tuning capabilities, utilizing a MoS₂/Sb₂Te₃ vdWs p-n heterojunction architecture designed explicitly for photodetection across the visible to near-infrared spectrum. These heterojunction devices provide ultra-low dark currents as small as 4.3 pA, a robust photoresponsivity of 0.12 A W⁻¹, and reasonable response times characterized by rising and falling durations of 0.197 s and 0.138 s, respectively. These novel devices exhibit remarkable tunability under the application of compressive strain up to 0.3%. The introduction of strain at the heterojunction interface influences the bandgap of the materials, resulting in a significant alteration of the heterojunction’s band structure. This subsequently shifts the detector’s optical absorption properties. The proposed strategy of strain-induced engineering of the stacked 2D crystal materials allows the tuning of the electronic and optical properties of the device. Such a technique enables fine-tuning of the optoelectronic performance of vdWs devices, paving the way for tunable high-performance, low-power consumption applications. This development also holds significant potential for applications in wearable sensor technology and flexible electro-optic circuits.

The exotic properties of two-dimensional materials and heterostructures, built by forming heterogeneous multi-layered stacks, have been widely explored across several subject matters following the goal to invent, design, and improve applications enabled by these materials. Successfully harvesting these unique properties effectively and increasing the yield of manufacturing two-dimensional material-based devices for achieving reliable and repeatable results is the current challenge. The scientific community has introduced various experimental transfer systems explained in detail for exfoliation of these materials; however, the field lacks statistical analysis and the capability of producing a transfer technique enabling (i) high transfer precision and yield, (ii) cross-contamination free transfer, (iii) multi-substrate transfer, and (iv) rapid prototyping without wet chemistry. Here, we introduce a novel two-dimensional material deterministic transfer system and experimentally show its high accuracy, reliability, repeatability, and non-contaminating transfer features by demonstrating fabrication of two-dimensional material-based optoelectronic devices featuring novel device physics and unique functionality. The system paves the way toward accelerated two-dimensional material-based device manufacturing and characterization. Such rapid and material analyzing prototype capability can accelerate not only layered materials science in discovery but also engineering innovations.

Arrays of photodetector‐based pixel sensors are ubiquitous in modern devices, such as smart phone cameras, automobiles, drones, laptops etc. Two‐dimensional (2D) material‐based photodetector arrays are a relevant candidate, especially for applications demanding planar form factors. However, shortcomings in pixel density and prototyping without cross contamination limit technology adoption and impact. Also, while 2D material detectors offer high absorption, graphene's closed bandgap results in undesirably high dark currents. Here, we introduce the experimental demonstration of dense planar photodetector arrays. We demonstrate a micrometer‐narrow pitched 2D detector pixels and show this approach's repeatability by verifying performing of a 16‐pixel detector array. Such dense and repeatable detector realization is enabled by a novel, selective, contamination‐free 2D material transfer system, that we report here in automated operation. The so realized photodetectors responsivity peaks at a high 0.8 A/W. Furthermore, we achieve uniform detector performance via bias voltage tuning calibration to maximize deployment. Lastly, we demonstrate 2D arrayed photodetectors not only on a silicon chip platform but verify array performance on flexible polymer substrates. Densley‐arrayed, flat, bendable, and uniform performing photodetector pixels enable emerging technologies in the space where lightweight and reliable performance is required, such as for the smart phone and emerging VR/AR markets, but also for smart gadgets, wearables, and also for size‐weight‐power‐constrained aviation and space platforms.

Here, we present a 40 GHz bandwidth electro-optic modulator with CMOS compatibility. Utilizing critical coupling modulation through induced loss in Si-ITO layers, the modulator offers high-speed operation and is suitable for photonics integrated systems and computing applications.

In integrated photonics, specific wavelengths are preferred such as 1550 nm due to low-loss transmission and the availability of optical gain in this spectral region. For chip-based photodetectors, layered two-dimensional (2D) materials bear scientific and technologically-relevant properties leading to strong light-matter-interaction devices due to effects such as reduced coulomb screening or excitonic states. However, no efficient photodetector in the telecommunication C-band using 2D materials has been realized yet. Here, we demonstrate a MoTe2-based photodetector featuring strong photoresponse (responsivity = 0.5 A/W) operating at 1550nm on silicon photonic waveguide enabled by engineering the strain (4%) inside the photo-absorbing transition-metal-dichalcogenide film. We show that an induced tensile strain of ~4% reduces the bandgap of MoTe2 by about 0.2 eV by microscopically measuring the work-function across the device. Unlike Graphene-based photodetectors relying on a gapless band structure, this semiconductor-2D material detector shows a ~100X improved dark current enabling an efficient noise-equivalent power of just 90 pW/Hz^0.5. Such strain-engineered integrated photodetector provides new opportunities for integrated optoelectronic systems.