Electro-optic metal–insulator–semiconductor–insulator–metal Mach-Zehnder plasmonic modulator

The performance of a CMOS-compatible electro-optic Mach-Zehnder plasmonic modulator is investigated using electromagnetic and carrier transport simulations. Each arm of the Mach-Zehnder device comprises a metal–insulator–semiconductor–insulator–metal (MISIM) structure on a buried oxide substrate. Quantum mechanical effects at the oxide/semiconductor interfaces were considered in the calculation of electron density profiles across the structure, in order to determine the refractive index distribution and its dependence on applied bias. This information was used in finite element simulations of the electromagnetic modes within the MISIM structure in order to determine the Mach-Zehnder arm lengths required to achieve destructive interference and the corresponding propagation loss incurred by the device. Both inversion and accumulation mode devices were investigated, and the layer thicknesses and height were adjusted to optimise the device performance. A device loss of <8 dB is predicted for a MISIM structure with a 25 nm thick silicon layer, for which the device length is <3 μm, and <5 dB loss is predicted for the limiting case of a 5 nm thick silicon layer in a 1.2 μm long device: in both cases, the maximum operating voltage is 7.5 V.     

Cross-shaped metal–semiconductor–metal plasmonic crystal for terahertz modulator

The transmission and tuning properties of a cross-shaped plasmonic crystal based on periodic metal–semiconductor–metal (MSM) structures have been investigated in the terahertz (THz) regime. According to the mode analysis, we find that the different resonance modes in the plasmonic crystal show the different changes when this device is actively controlled by the carrier injection of the MSM structures. The longitudinal modes disappear, while the horizontal mode moves to a higher frequency. The former leads to an intensity modulation at 0.5 THz and 1.1 THz when the groove depth h = 60 μm, and the later leads to a band blue-shift from 1.325 THz to 1.38 THz. These results will be applied to THz modulation and tunable filtering.     

Plasmonic modulator based on gain-assisted metal–semiconductor–metal waveguide

We investigate plasmonic modulators with gain material to be implemented as ultra-compact and ultra-fast active nanodevices in photonic integrated circuits. We analyze metal–semiconductor–metal (MSM) waveguides with InGaAsP-based active material layers as ultra-compact plasmonic modulators. The modulation is performed by changing the gain of the core, that results in different transmittance through the waveguides. A MSM waveguide enables high field localization and therefore high modulation speed. Bulk semiconductor, quantum wells and quantum dots, arranged in either horizontal or vertical layout, are considered as the core of the MSM waveguide. Dependences on the waveguide core size and gain values of various active materials are studied. The designs consider also practical aspects like n- and p-doped layers and barriers in order to obtain close to reality results. The effective propagation constants in the MSM waveguides are calculated numerically. Their changes in the switching process are considered as a figure of merit. We show that a MSM waveguide with electrical current control of the gain incorporates compactness and deep modulation along with having a reasonable level of transmittance.     

Plasmonic finite-thickness metal–semiconductor–metal waveguide as ultra-compact modulator

We propose a plasmonic waveguide with semiconductor gain material for optoelectronic integrated circuits. We analyze properties of a finite-thickness metal–semiconductor–metal (F-MSM) waveguide to be utilized as an ultra-compact and fast plasmonic modulator. The InP-based semiconductor core allows electrical control of signal propagation. By pumping the core we can vary the gain level and thus the transmittance of the whole system. The study of the device was made using both analytical approaches for planar two-dimensional case as well as numerical simulations for finite-width waveguides. We analyze the eigenmodes of the F-MSM waveguide, propagation constant, confinement factor, Purcell factor, absorption coefficient, and extinction ratio of the structure. We show that using thin metal layers instead of thick ones we can obtain higher extinction ratio of the device.     

Gate-modulated generation–recombination current in n-type metal–oxide–semiconductor field-effect transistor

Gate-modulated generation–recombination（GMGR） current IGMGRinduced by the interface traps in an n-type metal–oxide–semiconductor field-effect transistor（n MOSFET） is investigated. The generation current is found to expand rightwards with increasing the reversed drain PN junction bias, and the recombination current is enhanced as the forward drain bias increases. The variations of IGMGRcurves are ascribed to the changes of the electron density and hole density at the interface, NSand PS, under the different drain bias voltages. Based on an analysis of the physical mechanism, the IGMGR model is set up by introducing two coefficients（m and t）. The coefficients m and t can modulate the curves widths and peak values. The simulated results under reverse mode and forward mode are obviously in agreement with the experimental results. This proves that this model can be applicable for generation current and recombination current and that the theory behind the model is reasonable. The details of the relevant mechanism are given in the paper.     

Multifunctional silicon-based light emitting device in standard complementary metal–oxide–semiconductor technology

A three-terminal silicon-based light emitting device is proposed and fabricated in standard 0.35 μ m complementary metal--oxide--semiconductor technology. This device is capable of versatile working modes: it can emit visible to near infra-red (NIR) light (the spectrum ranges from 500 nm to 1000 nm) in reverse bias avalanche breakdown mode with working voltage between 8.35 V--12 V and emit NIR light (the spectrum ranges from 900 nm to 1300 nm) in the forward injection mode with working voltage below 2 V. An apparent modulation effect on the light intensity from the polysilicon gate is observed in the forward injection mode. Furthermore, when the gate oxide is broken down, NIR light is emitted from the polysilicon/oxide/silicon structure. Optoelectronic characteristics of the device working in different modes are measured and compared. The mechanisms behind these different emissions are explored.     

Hydrogen interaction with GaN metal–insulator–semiconductor diodes

Interaction mechanism of hydrogen with GaN metal–insulator–semiconductor (MIS) diodes is investigated, focusing on the metal/semiconductor interfaces. For MIS Pt-GaN diodes with a SiO₂ dielectric, the current–voltage (I–V) characteristics reveal that hydrogen changes the conduction mechanisms from Fowler–Nordheim tunneling to Poole–Frenkel emission. In sharp contrast, Pt-Si_xN_y-GaN diodes exhibit Poole–Frenkel emission in nitrogen and do not show any change in the conduction mechanism upon exposure to hydrogen. The capacitance–voltage (C–V) study suggests that the work function change of the Schottky metal is not responsible mechanism for the hydrogen sensitivity.     

A wire-form emitter metal–insulator–semiconductor tunnel junction

Physical effects arising due to change of configuration of a MIS system from planar to cylindrical, are theoretically analyzed. Attention is paid to the voltage partitioning and all the components of tunneling current. A simple simulation model is developed enabling prediction of the band diagram details and calculation of the currents. The trends expected with decreasing system radius are elucidated. Cylindrical geometry can be faced with when quantum wire is used as an electron emitter. Similar form may also be roughly attributed to an edge region of conventional MIS capacitors.     

Fullerene-based electrode interlayers for bandgap tunable organometal perovskite metal–semiconductor–metal photodetectors

Perovskite photoconductor-type photodetector with metal–semiconductor–metal(MSM) structure is a basic device for photodetection applications. However, the role of electrode interlayer in MSM-type perovskite devices is less investigated compared to that of the pin diode structure. Here, a systematic investigation on the influence of phenyl-C_(61)-butyric acid methyl ester(PCBM) and indene-C_(60) bisadduct(ICBA) interfacial layers for MSM perovskite photodetectors is reported.It is found that the fullerene-based interlayer significantly enhances the photocurrent of the MSM photodetectors. On one hand, the PCBM interlayer is more suitable for CH_3 NH_3 PbI_3 photodetector, with the responsivity two times higher than that of the device with ICBA interlayer. The ICBA layer, on the other hand, becomes more effective when the band gap of perovskite is enlarged with bromine composition, denoted as CH_3 NH_3 Pb(I_(1-x)Br_x)_3(0 ≤ x ≤1). It is further found that the specific detectivity of photodetectors with ICBA interlayer becomes even higher than those with PCBM when the bromine compositional percentage reaches 0.6(x 0.6).     

Investigation on latch-up susceptibility induced by high-power microwave in complementary metal–oxide–semiconductor inverter

The latch-up effect induced by high-power microwave(HPM) in complementary metal–oxide–semiconductor(CMOS) inverter is investigated in simulation and theory in this paper. The physical mechanisms of excess carrier injection and HPM-induced latch-up are proposed. Analysis on upset characteristic under pulsed wave reveals increasing susceptibility under shorter-width pulsed wave which satisfies experimental data, and the dependence of upset threshold on pulse repetitive frequency(PRF) is believed to be due to the accumulation of excess carriers. Moreover, the trend that HPMinduced latch-up is more likely to happen in shallow-well device is proposed.Finally, the process of self-recovery which is ever-reported in experiment with its correlation with supply voltage and power level is elaborated, and the conclusions are consistent with reported experimental results.     

Analysis of interface states and series resistance for Al/PVA:n-CdS nanocomposite metal–semiconductor and metal–insulator–semiconductor diode structures

This paper presents the fabrication and characterization of Al/PVA:n-CdS (MS) and Al/Al₂O₃/PVA:n-CdS (MIS) diode. The effects of interfacial insulator layer, interface states (N _ss ) and series resistance (R _s ) on the electrical characteristics of Al/PVA:n-CdS structures have been investigated using forward and reverse bias I–V, C–V, and G/w–V characteristics at room temperature. Al/PVA:n-CdS diode is fabricated with and without insulator Al₂O₃ layer to explain the effect of insulator layer on main electrical parameters. The values of the ideality factor (n), series resistance (R _s ) and barrier height (? _b ) are calculated from ln(I) vs. V plots, by the Cheung and Norde methods. The energy density distribution profile of the interface states is obtained from the forward bias I–V data by taking into account the bias dependence ideality factor (n(V)) and effective barrier height (? _e ) for MS and MIS diode. The N _ss values increase from mid-gap energy of CdS to the bottom of the conductance band edge for both MS and MIS diode.     

Pressure induced magnetic and semiconductor–metal phase transitions in Cr_2MoO_6

We investigate magnetic ordering and electronic structures of Cr_2MoO_6under hydrostatic pressure. To overcome the band gap problem, the modified Becke and Johnson exchange potential is used to investigate the electronic structures of Cr_2MoO_6. The insulating nature at the experimental crystal structure is produced, with a band gap of 1.04 eV, and the magnetic moment of the Cr atom is 2.50 μB, compared to an experimental value of about 2.47 μB. The calculated results show that an antiferromagnetic inter-bilayer coupling–ferromagnetic intra-bilayer coupling to a ferromagnetic inter-bilayer coupling–antiferromagnetic intra-bilayer coupling phase transition is produced with the pressure increasing. The magnetic phase transition is simultaneously accompanied by a semiconductor–metal phase transition. The magnetic phase transition can be explained by the Mo–O hybridization strength, and ferromagnetic coupling between two Cr atoms can be understood by empty Mo-d bands perturbing the nearest O-p orbital.     

Geometry and material optimization of the extraordinary magnetoresistance in the semiconductor–metal hybrid structure

The effects of geometry and material parameters on the extraordinary magnetoresistance (EMR) of the rectangular semiconductor–metal hybrid structure have been studied systematically using the finite-element method (FEM). We find that the EMR depends sensitively on the placement of the voltage probes and explain the origin of the EMR enhancement in the asymmetric voltage probe configuration. The width of the metal is important for the EMR effect as well as the width of the semiconductor. The low-field EMR shows an approximate quadratic with the mobility of semiconductor, while the high-field EMR gradually saturates with the increase of mobility due to the little change of hall angle. To obtain significant EMR effect, the ration of conductivity of metal and semiconductor should be larger than 10⁴${10}^4$.     

Effect of laser intensity on the semiconductor–metal transition in a doped Quantum Well

We demonstrate laser induced semiconductor–metal transition through an abrupt change in diamagnetic susceptibility of a donor at critical concentration in a GaAs/Al_xGa_1−xAs Quantum Well for finite barrier model in the effective mass approximation using variational principle. We have considered Anderson‘s localization due to the random distribution of impurities in our calculation. The nonparabolicity of the conduction band is also considered. Our results without laser field agree with the earlier theoretical results and also with the recent experimental results.