Conduction and rectification in NbOx- and NiO-based metal-insulator-metal diodes

Abstract

Conduction and rectification in nanoantenna-coupled NbOx- and NiO-based metal-insulator-metal (MIM) diodes (“nanorectennas”) are studied by comparing new theoretical predictions with the measured response of nanorectenna arrays. A new quantum mechanical model is reported and agrees with measurements of current–voltage (I–V) curves, over 10 orders of magnitude in current density, from [NbOx(native)-Nb2O5]- and NiO-based samples with oxide thicknesses in the range of 5–36 nm. The model, which introduces new physics and features, including temperature, electron effective mass, and image potential effects using the pseudobarrier technique, improves upon widely used earlier models, calculates the MIM diode's I–V curve, and predicts quantitatively the rectification responsivity of high frequency voltages generated in a coupled nanoantenna array by visible/near-infrared light. The model applies both at the higher frequencies, when high-energy photons are incident, and at lower frequencies, when the formula for classical rectification, involving derivatives of the I–V curve, may be used. The rectified low-frequency direct current is well-predicted in this work's model, but not by fitting the experimentally measured I–V curve with a polynomial or by using the older Simmons model (as shown herein). By fitting the measured I–V curves with our model, the barrier heights in Nb-(NbOx(native)-Nb2O5)-Pt and Ni-NiO-Ti/Ag diodes are found to be 0.41/0.77 and 0.38/0.39 eV, respectively, similar to literature reports, but with effective mass much lower than the free space value. The NbOx (native)-Nb2O5 dielectric properties improve, and the effective Pt-Nb2O5 barrier height increases as the oxide thickness increases. An observation of direct current of ∼4 nA for normally incident, focused 514 nm continuous wave laser beams are reported, similar in magnitude to recent reports. This measured direct current is compared to the prediction for rectified direct current, given by the rectification responsivity, calculated from the I–V curve times input power.

Review—Beyond the Highs and Lows: A Perspective on the Future of Dielectrics Research for Nanoelectronic Devices

“…A number of thin film single insulator MIM diode systems have been investigated. 76,[506][507][508][509][510][511][512][517][518][519][520][521]524,526,[537][538][539][540]581,[590][591][592][593][594][595][596][597] Despite this extensive work on MIM devices, the traditional approach of using dissimilar metal electrodes to achieve rectification is limited by M and by the properties (ϕ Bn's and charge transport mechanisms) of the single insulator. For example, while narrow E G insulators may suffer from thermionic based conduction and higher dielectric constant, wide E G insulators may be limited by high V ON and high zero bias resistance.…”

Nanorectenna spectrally-selective plasmonic hot electron response to visible-light lasers

“…Nonlinear detectors and nonlinear optics require a nonlinear material with an ideally highly nonlinear diode-like current-voltage (I-V ) characteristic and its conversion of a single-frequency input voltage to a rectified output current that contains multiple frequency components, including twice the original harmonic and direct current (zero frequency), shown schematically in figure 1. In [5], the CCDC-Soldier Center (CCDC-SC) designed, characterized, modeled, and analyzed such a rectifying diode, in order to predict (micro) rectenna responsivity (usually given in Amperes/Watt, or microrectenna output current divided by incident power). This metal-insulator-metal (MIM) diode, where conduction occurs from one metal layer (the left-hand of figure 2(a) or '−' side, with the larger barrier height), to the opposite ('+' side in figure 2(a), with the smaller barrier height) through a barrier layer that has a conduction band separated from the Fermi energies by an amount called the barrier height (generally is different on either side of the barrier layer), has the electrical asymmetry, as well as nonlinearity, that is needed to rectify.…”

“…In the infrared regime, dimensions can be somewhat larger and the RC time constant requirement is somewhat easier to satisfy, then in the visible regime. Figure 2 illustrates MIM diodes coupled to antenna arrays, the subject of a CCDC-SC research program [5]. In experimental measurements, significant output power was first observed in response to visible (514 nm) illumination of nanorectenna arrays [5].…”

“…Figure 2 illustrates MIM diodes coupled to antenna arrays, the subject of a CCDC-SC research program [5]. In experimental measurements, significant output power was first observed in response to visible (514 nm) illumination of nanorectenna arrays [5]. Intriguingly, it was greater than when illuminated by a shorter wavelength, where a greater tunneling probability can be expected for electrons photo-excited to a higher energy.…”

“…For understanding the key parameters and process, modeling was accomplished by using a quantum mechanical model of MIM diode conduction via both quantum tunneling and thermionic conduction mechanisms, which incorporated new physics and improved on early models, dating back to the 1960s, of these rectifying diodes [5].…”