Geometric Diode Research Articles

Analysis of MIM geometric tunnel diode in optical rectenna system that using spectrally controlled thermal radiation

Analysis of MIM geometric tunnel diode in optical rectenna system that using spectrally controlled thermal radiation

Additional electric field in real trench MOS barrier Schottky diode

In real trench MOS barrier Schottky diode (TMBS diode) additional electric field (AEF) the whole is formed in the near contact region of the semiconductor and its propagation space is limited with the barrier metal and the metallic electrodes of MOS structures. Effective potential barrier height TMBS diode is formed via resulting electric field of superposition AEF and electric field of space charge region (SCR) semiconductor. The dependence of the resulting electric field intensity of the distance towards the inside the semiconductor is nonlinear and characterized by a peak at a certain distance from the interface. The thickness of the SCR in TMBS diode becomes equal to the trench depth. Force and energy parameters of the AEF, and thus resulting electric field in the SCR region, become dependent on the geometric design parameters TMBS diode. The forward I-V characteristic TMBS diode is described by the thermionic emission theory as in conventional flat Scottky diode, and in the reverse bias, current is virtually absent at initial voltage, appears abruptly at a certain critical voltage.

High Performance Room Temperature Rectenna IR Detectors Using Graphene Geometric Diodes

High performance rectenna detectors that operate at room temperature have been developed for the frequency range of terahertz to infrared (IR). We formed IR rectennas by coupling bowtie antennas to ultrafast diodes, called geometric diodes. Geometric diodes rely on geometric asymmetry and the long charge carrier mean-free path length of graphene to provide asymmetric current-voltage characteristics. The planar structure of the geometric diode provides the femtosecond RC time constant necessary for detection of IR frequencies. Fabricated IR rectennas using graphene geometric diodes have shown strong optical response to 28 THz CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser illumination at room temperature. The detectivity (D*) and the noise equivalent power (NEP) of the IR rectennas are calculated to be on the order of 108 cm Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-9</sup> W Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1/2</sup> , respectively. Simulations show that with some improvement room temperature rectennas using graphene geometric diodes are able to achieve an NEP value as low as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> W Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1/2</sup> .

Non-reciprocal geometric wave diode by engineering asymmetric shapes of nonlinear materials.

Unidirectional nonreciprocal transport is at the heart of many fundamental problems and applications in both science and technology. Here we study the novel design of wave diode devices by engineering asymmetric shapes of nonlinear materials to realize the function of non-reciprocal wave propagations. We first show analytical results revealing that both nonlinearity and asymmetry are necessary to induce such non-reciprocal (asymmetric) wave propagations. Detailed numerical simulations are further performed for a more realistic geometric wave diode model with typical asymmetric shape, where good non-reciprocal wave diode effect is demonstrated. Finally, we discuss the scalability of geometric wave diodes. The results open a flexible way for designing wave diodes efficiently simply through shape engineering of nonlinear materials, which may find broad implications in controlling energy, mass and information transports.

Graphene geometric diodes for terahertz rectennas

We demonstrate a new thin-film graphene diode called a geometric diode that relies on geometric asymmetry to provide rectification at 28 THz. The geometric diode is coupled to an optical antenna to form a rectenna that rectifies incoming radiation. This is the first reported graphene-based antenna-coupled diode working at 28 THz, and potentially at optical frequencies. The planar structure of the geometric diode provides a low RC time constant, on the order of 10−15 s, required for operation at optical frequencies, and a low impedance for efficient power transfer from the antenna. Fabricated geometric diodes show asymmetric current–voltage characteristics consistent with Monte Carlo simulations for the devices. Rectennas employing the geometric diode coupled to metal and graphene antennas rectify 10.6 µm radiation, corresponding to an operating frequency of 28 THz. The graphene bowtie antenna is the first demonstrated functional antenna made using graphene. Its response indicates that graphene is a suitable terahertz resonator material. Applications for this terahertz diode include terahertz-wave and optical detection, ultra-high-speed electronics and optical power conversion.

Ultrahigh speed graphene diode with reversible polarity

The ability to tune the carrier-type concentration ratio with applied field along with a mean-free path length approaching 1μm in graphene enables a new diode in which the diode polarity can be reversed. The diode consists of a thin graphene film with a geometric asymmetry that determines a preferred direction for charge-carrier transport, independent of whether the carriers are electrons or holes. We fabricated submicron geometric diodes by patterning and etching exfoliated graphene. Applying field-effect voltages to the substrate, we reversed the carrier type and demonstrated reversal of the diode polarity. The graphene geometric diodes exhibited rectification at 28THz, opening the way to ultrahigh speed applications for these versatile devices.