P. S. Menon

An analysis of silicon waveguide phase modulation efficiency based on carrier depletion effect

This paper highlights the study of carrier depletion effect on silicon waveguide with p-i-n diode and NPN structure. The device performance is predicted by using 2D Silvaco CAD software under different applied voltages. Device performances in terms of modulation efficiency will be discussed.

Design and optimization of 22 nm gate length high-k/metal gate NMOS transistor

In this paper, we invented the optimization experiment design of a 22 nm gate length NMOS device which uses a combination of high-k material and metal as the gate which was numerically developed using an industrial-based simulator. The high-k material is Titanium dioxide (TiO2), while the metal gate is Tungsten Silicide (WSix). The design is optimized using the L9 Taguchi method to get the optimum parameter design. There are four process parameters and two noise parameters which were varied for analyzing the effect on the threshold voltage (Vth). The objective of this experiment is to minimize the variance of Vth where Taguchis nominal-the-best signal-to-noise ratio (S/N Ratio) was used. The best settings of the process parameters were determined using Analysis of Mean (ANOM) and analysis of variance (ANOVA) to reduce the variability of Vth. The results show that the Vth values have least variance and the mean value can be adjusted to 0.306V ±0.027 for the NMOS device which is in line with projections by the ITRS specifications.

Design and modeling of a vertical-cavity surface-emitting laser (VCSEL)

In this paper, we attempt to design, simulate and characterize an InGaAs-based vertical-cavity surface-emitting laser (VCSEL) employing InGaAsP multi-quantum wells sandwiched between GaAs/AlGaAs and GaAs/AlAs distributed Bragg reflectors using an industrial-based numerical simulator. We were able to obtain a working model at an optical wavelength of 1.55 mum. This paper provides key results of the device characteristics including the DC V-I and the light power versus electrical current. Effect of DBR mirror stack quantities were also experimented with and the results are reported here.

DESIGN AND CHARACTERIZATION OF MULTIPLE COUPLED MICRORING BASED WAVELENGTH DEMULTIPLEXER IN SILICON–ON–INSULATOR (SOI)

We report in this paper, an optimized design and characterization of SOI based single mode, four channels wavelength demultiplexer using microrings. The usage of silicon-on-insulator (SOI) allows a wide free spectral range (FSR) for the device that is crucial in developing ultra-compact integrations of planar lightwave circuits (PLCs). The characterizations are done using Finite-Difference Time-Domain (FDTD) mode simulations from RSOFT. Serially cascaded microring arrays up to the third order are presented to study the design trade-off among the FSR, Q-factor and optical losses of the laterally coupled wavelength demultiplexer. The demultiplexer is expected to be working at C-band region of Wavelength Division Multilplexing (WDM) for a wavelength around 1550 nm. Our proposed demultiplexer has low insertion loss (< 0.5 dB) and a crosstalk around 12 ~ 19 dB.

Threshold voltage optimization in a 22nm High-k/Salicide PMOS device

In this article, we examine the effect of four process parameters and two noise parameters on the threshold voltage (Vth) of a 22nm gate length PMOS device. The gate of the device uses titanium dioxide (TiO2) as the high permittivity material (high-k) layer to replace the traditional silicon dioxide (SiO2) dielectric layer. While the polysilicon (poly-Si) which is also known as self-aligned silicide (SALICIDE) layer, is deposited on top of the high-k dielectric layer and is used to reduce the gate electrode resistance. The virtual fabrication device was designed using the ATHENA and electrical characterization was simulated using ATLAS. These two simulators were combined with the L9 Taguchis experimental design to aid in the design and optimization of the process parameters for a total of 36 simulation runs. The objective is to minimize the variance in Vth using Taguchis nominal-the-best signal-to-noise ratio (SNR) analysis. Analysis of the mean (ANOM) was used to determine the best settings for the process parameters while Analysis of variance (ANOVA) was used to reduce the variability of Vth. The results show that the Vth values with the least variance is -0.289 V ± 12.7% which is well within the prediction by the International Technology Roadmap for Semiconductors (ITRS) 2011.

Impact of coupled resonator geometry on silicon-on insulator wavelength filter characteristics

We have analyzed and discussed the issues arising in the design of Silicon — on — Insulator (SOI) wavelength filters with different types of device geometry. Microring and microdisk geometries have been chosen as the device configurations and in order to demonstrate the device performance and potential, Free Spectral Range (FSR), and Q-factor values are computed. Studies of the transmittance characteristics are carried out using Finite-Difference Time-Domain (FDTD) methods by RSOFT Software. Results show that the microring-based wavelength filter has a FSR of 1.4 THz and a Q-factor value of 486. On the other hand, the microdisk based filter has a broader FSR with slightly smaller Q-factor.

Statistical process modelling for 32nm high-K/metal gate PMOS device

The evolution of MOSFET technology has been governed solely by device scaling, delivered an ever-increasing transistor density through Moores Law. In this paper, the design, fabrication and characterization of 32nm HfO₂/TiSi₂ PMOS device is presented; replacing the conventional SiO₂ dielectric and Poly-Silicon. The fabrication and simulation of PMOS transistor is performed via Virtual Wafer Fabrication (VWF) Silvaco TCAD Tools namely ATHENA and ATLAS. Taguchi L9 Orthogonal method is then applied to this experiment for optimization of threshold voltage (V_TH) and leakage current (I_OFF). The simulation result shows that the optimal value of V_TH and I_OFF which are 0.1030075V and 3.4264075×10^-12A/um respectively are well within ITRS prediction.

Investigation on Optical Interconnect(OI) link performance using external modulator

This paper investigates and analyzes an Optical Interconnect (OI) link using external (indirect) modulation technique. A Continuous Wave (CW) light source with a Mach Zehnder (MZ) modulator is used in the transmitter part and a Si-based waveguide is used as a transmission path. Indium Gallium Arsenide (InGaAs) and Germanium (Ge) materials were applied to observe the performance of Avalanche Photodiode (APD) and P-I-N Photodiode (PIN). In order to evaluate the performance of OI link using external (indirect) modulation, the model of OI link was designed and simulated using OptiSPICE tools. Simulation results on the performance of MZ modulator, power degradation of OI link and receiver sensitivity are reported in this paper.

NEAR FIELD AND FAR FIELD EFFECTS IN THE TAGUCHI-OPTIMIZED DESIGN OF AN InP/GaAs-BASED DOUBLE WAFER-FUSED MQW LONG-WAVELENGTH VERTICAL-CAVITY SURFACE-EMITTING LASER

Long-wavelength VCSELs (LW-VCSEL) operating in the 1.55 μm wavelength regime offer the advantages of low dispersion and optical loss in fiber optic transmission systems which are crucial in increasing data transmission speed and reducing implementation cost of fiber-to-the-home (FTTH) access networks. LW-VCSELs are attractive light sources because they offer unique features such as low power consumption, narrow beam divergence and ease of fabrication for two-dimensional arrays. This paper compares the near field and far field effects of the numerically investigated LW-VCSEL for various design parameters of the device. The optical intensity profile far from the device surface, in the Fraunhofer region, is important for the optical coupling of the laser with other optical components. The near field pattern is obtained from the structure output whereas the far-field pattern is essentially a two-dimensional fast Fourier Transform (FFT) of the near-field pattern. Design parameters such as the number of wells in the multi-quantum-well (MQW) region, the thickness of the MQW and the effect of using Taguchis orthogonal array method to optimize the device design parameters on the near/far field patterns are evaluated in this paper. We have successfully increased the peak lasing power from an initial 4.84 mW to 12.38 mW at a bias voltage of 2 V and optical wavelength of 1.55 μm using Taguchis orthogonal array. As a result of the Taguchi optimization and fine tuning, the device threshold current is found to increase along with a slight decrease in the modulation speed due to increased device widths.

Peak power and wavelength optimization of a double-fused LW-VCSEL

Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) have profound advantages over the traditional edge-emitting lasers offering improved properties with respect to mode selectivity, fiber coupling, threshold currents and integration into 2D arrays or with other electronic devices. Its commercialization is gaining momentum as the local and access network in optical communication system expands. This paper reports the optimization of the peak lasing power and peak lasing wavelength of a LW-VCSEL using a numerical-based simulator and Taguchis orthogonal array methodology. Initially, peak lasing power increment of 96.5% was achieved at 9.51 mW with peak wavelength of 1.55956 µm. Next, we attempted to bring the peak wavelength on target to 1.55 µm. It was found that a reduction of DBR mirror thicknesses by 1.3% from its nominal values is able to produce a device with lasing powers of 11.62 mW and on-target peak wavelength of 1.55 µm.