We present a fabricated metal-semiconductor-metal (MSM) photodetector exhibiting an enhanced photocurrent by integrating a nanoscale metallic grating into its contacts. This serves to increase the incident photon flux about the aperture of the device by guiding incident photons as surface plasmon polaritons. High speed time response data shows that the device responsivity may be increased without sacrificing speed. We demonstrate both a photocurrent enhancement and responsivity increase of about 90% at the design wavelength in comparison to otherwise identical MSM photodetectors without integrated nanoscale gratings. The device retains the MSM advantages of simplicity, planarity, and monolithic integrability.

A simple room‐temperature process of depositing MXene on a III‐V structure with embedded 2D electron gas (2DEG) is used, which results in a large area, , photodetector (PD) device that greatly outperforms vacuum deposited Ti/Au metal‐semiconductor‐metal (MSM) PD's. By co‐optimizing properties of 2D MXene contacts and the III‐V material heterojunctions, this device sets new operating records with responsivity up to 1.04 A W^‐1 at low optical powers, corresponding to >230% internal quantum efficiency, dark current of 50 , >105.6‐dB dynamic range, and 25–150 ps response time, which improves the previous MXene‐Semiconductor‐MXene responsivity by >2.7 times and is 7 × 10³ –−10⁶ times faster compared to other MXene‐based PDs. This is achieved by enhancing the Schottky barrier height by forming a Van der Waals (vdW) heterojunction between a wide bandgap AlGaAs surface layer and spin coated Ti₃C₂T_z electrodes. A layered architecture transports the optically generated electrons to a 2DEG channel at the GaAs/AlGaAs heterointerface, where they are rapidly collected. The landscaped electric field pushes the slow holes to an underlying low temperature‐grown GaAs (LT‐GaAs) region where they recombine. The proposed Schottky‐2DEG Photoconductor‐Schottky model for device operation shows how this device circumvents the canonical limitations of gain‐bandwidth product, and carrier transit time, while replacing the need for vacuum deposition of gold or other precious metals.

Moderation of internal quantum mechanical energies, such as exchange energy of an unconventional contact, comprised of a system of 2-D charge carriers, improves performance merits of variable capacitors, varactors, mainly in tuning ratio (TR), and sensitivity, S. Energy transfer from the unconventional contact to the dielectric increases the energy density and enhances the capacitance of the varactor. Here, we analyze the performance of an unconventional varactor based on a planar metal-semiconductor-metal (MSM) structure with an embedded layer of high-density 2-D electron gas (2DEG). Through localized field-assisted manipulation of the 2DEG density, a twice larger equilibrium capacitance and a minimum capacitance, less than the geometric capacitance of a conventional MSM, are achieved. Moreover, the maximum capacitance increases through a Batman-shaped capacitance enhancement at a threshold voltage. Therefore, giant is attained while maintaining quality factors of up to 30. Capacitance-voltage characteristics exhibit a switched-capacitor behavior with S as high as 350 that is due to localized transitions from a dense 2DEG to a complete depletion. This MSM 2-D varactor combines the unconventional features of 2DEG with superior electrical properties of MSMs.

The electron cloud that is formed in the narrow gap material in a modulation-doped heterostructure affects the Schottky contact made to the wide gap material. It also influences absorption and collection of the optically generated carriers. Photocurrent spectra, current–voltage, and current–temperature measurements show that the increase in electron cloud density decreases dark current flow while increasing photoresponsivity. We propose that the Coulombic interaction between the confined electron cloud and the emitted electrons from metal to the wide gap material increases the barrier height. The electric field in the direction of growth due to modulation doping accounts for the increase in photoelectron collection efficiency. Implementation of this effect increases efficiency of photodetectors while, simultaneously, reducing the noise due to dark current.

We report on a variable capacitor that is formed between Schottky contacts and the two dimensional electron gas (2DEG) in a planar metal-semiconductor-metal structure. Device capacitance at low bias is twice the series capacitance of anode and cathode, enhancing to a maximum value, Cmax, at a threshold voltage, before reaching a minimum, Cmin, lower than the geometric capacitance of the coplanar contacts, thus resulting in ultra high Cmax/Cmin tuning ratio. Sensitivity, the normalized change of capacitance with voltage, is also very large. The dense reservoir of the 2DEG charge maintained between contacts is shown to be responsible for this remarkable performance.