Susan K. Earles

Variation in efficiency with change in band gap and thickness in thin film amorphous silicon tandem heterojunction solar cells with AFORS-HET

Numerical simulation of both single and double absorbing layers in amorphous silicon thin film solar cell is performed with the use of AFORS-HET. A single absorbing layer solar cell with both a-SiH and a-SiGeH is designed and compared with a tandem heterojunction solar cell, a-SiC/a-SiH/a-Si(i)/a-SiGeH. Design parameters are investigated, compared and optimized. The maximum efficiency for each single absorbing layer and for a tandem heterojunction thin film solar cell, a-SiC/a-SiH/a-Si(i)/a-SiGeH, is predicted. The results are validated by comparing with two different method of analysis.

Computer analysis of microcrystalline silicon hetero-junction solar cell with lumerical FDTD/DEVICE

The computer analysis of tandem solar cell, c-Si/a-Si:H/μc-SiGe, is studied within Lumerical FDTD/Device 4.6. The optical characterization is performed in FDTD and then total generation rate is tra...

A novel method for generating a low temperature coefficient (TC) reference voltage from high TC reference cells to achieve wide temperature stability for remote sensors

This paper presents a novel functional block level abstraction for generating a stable reference voltage over a wide temperature range. The proposed method uses multiple high temperature coefficient (TC) reference sources to generates a low TC voltage. The proposed approach is demonstrated using four BiCMOS voltage reference cells, with 26.6ppm/C TC as an example to achieve 1.24ppm/C TC over a temperature range from −35°C to 160°C which is about 95% decrease in TC as per the simulated values. The proposed solution can be scaled to employ multiple cost effective, non-ideal reference voltage generators with high TC and shorter temperature range, to produce a reference voltage with a low TC over wider temperature range for various applications including bionics and deep space vehicles.

Variation in Efficiency with Respect to Change in Band Gap and Thickness in Thin Film Amorphous Silicon Tandem Heterojunction Solar Cells with AFORS-HET

Simulation of an amorphous silicon heterojunction thin film solar cell is performed. It is designed as a-SiC/a-Si(i)/a-Si:H/ and a-SiC/a-Si(i)/a-SiGe:H for optimizing of device parameters and increasing the efficiency.

Fiber-Optic Fabry-Perot Phase Shifted Interferometer Using Modal Demultiplexing

A fiber-optic phase-shifted Fabry-Perot interferometer (PS-FPI) using a modal phase shifter (MPS) and modal demultiplexing is demonstrated. The PS-FPI is used as a temperature sensor to obtain two output fringe sets as a result of a 6°C rise in temperature. A controllable phase shift between the fringe sets is obtained using the MPS and is beneficial in quadrature demodulation of measurand induced sensor signals which can extend the unambiguous range beyond half a fringe. Located before the sensing cavity, the MPS introduces a phase shift between the LP01 and LP11 modes. These modes travel to the FP cavity to produce interference fringes. This results in a few-mode sensor system having 2 orders of magnitude higher sensitivity than conventional few-mode systems, with a worst case voltage signal to noise ratio of 16.9 dB for a 0.5°C rise in temperature.

A novel circuit to achieve high linearity in power amplifiers for WCDMA cellular base transceiver stations

This paper presents a novel circuit to minimize the third order intermodulation distortion component and thus improves the linearity of power amplifiers. The circuit utilizes the nonlinear base-collector and base-emitter diode capacitances of a transistor biased in the saturation region to provide a nonlinear feedback path between the output and input of the amplifier. This concept was implemented in the design of a two watt power amplifier in InGaP/GaAs heterojunction bipolar transistor process. The design demonstrated 51 dBm of output third order intercept point at 17 dBm/tone output power level at 2140 MHz in the WCDMA band. The output P1dB was measured to be about 32 dBm. The amplifier is externally matched, thus provides flexibility to optimize the amplifier across a specific frequency band of interest between 400 MHz and 2700 MHz.

Design of a two watt power amplifier in InGaP/GaAs HBT process for very high linearity wireless applications

This paper presents the design of a very high linearity two watt power/driver amplifier in InGaP/GaAs Heterojunction Bipolar Transistor (HBT) technology for wireless standards like WCDMA. High linearity was achieved through a novel circuit that minimizes the third order intermodulation distortion component in the output signal. The circuit utilizes the base-collector and base-emitter diode capacitances of a transistor biased in the saturation region to provide a nonlinear feedback path between the output and input of the amplifier. In the 2.14GHz WCDMA band, the amplifier demonstrated 51dBm of output third order intercept point at 17dBm/tone output power level with output 1dB compression point of about 32dBm The amplifier is externally matched, thus provides flexibility to optimize the amplifier across a specific frequency band of interest between 400MHz and 2700MHz.

Characterization of aluminum, brass and steel nanoparticles after laser ablation

Understanding the surface properties of materials at the atomic-scale level is of keen interest in advanced materials processing. An interdepartmental research group at Florida Institute of Technology is currently ablating samples using a state-of-the-art ultra-short pulse (USP) laser to create nanostructures. USP lasers are unique in that they can be used to modify or machine any substance in an almost athermal ablation process, independent of melt point or composition, due to the physics of non-linear optical absorption.This paper focuses on three metals: Aluminum, Brass and Steel and on analyzing the nanoparticles created on each sample. Laser parameters, e.g., pulse energy, repetition rate, and number of laser runs are varied to optimize the ablation process. Scanning Electron Microscopy and Scanning Probe Microscopy were used to create images of the samples. SPM proprietary software then was used to process the images and to analyze the surfaces to determine nanostructure size, composition and surface roughness. The original SPM images were then processed again, but this time using F.I.T.’s proprietary flattening algorithm and MATLAB filters. The two image processing techniques and statistical roughness parameters were then compared.This research will culminate in a materials library that will be accessible to researchers in the academic, military and commercial sectors.Understanding the surface properties of materials at the atomic-scale level is of keen interest in advanced materials processing. An interdepartmental research group at Florida Institute of Technology is currently ablating samples using a state-of-the-art ultra-short pulse (USP) laser to create nanostructures. USP lasers are unique in that they can be used to modify or machine any substance in an almost athermal ablation process, independent of melt point or composition, due to the physics of non-linear optical absorption.This paper focuses on three metals: Aluminum, Brass and Steel and on analyzing the nanoparticles created on each sample. Laser parameters, e.g., pulse energy, repetition rate, and number of laser runs are varied to optimize the ablation process. Scanning Electron Microscopy and Scanning Probe Microscopy were used to create images of the samples. SPM proprietary software then was used to process the images and to analyze the surfaces to determine nanostructure size, composition and surfac...

Hydrogen sensor using optical reflectance from porous silicon with a palladium thin film

Results of a hydrogen sensor based on light scattering from a porous silicon surface coated with a thin palladium film are discussed. Reflected light scattered from the rough surface of porous silicon surface with a thin palladium film is compared before and after exposure to hydrogen gas. After exposure to hydrogen gas the sensors optical reflectance is decreased indicating the presence of hydrogen.

Porous silicon surface feature size estimation using the reflectance spectrum

In this paper we excite the surface of porous silicon with incoherent, broad band white light and observe the spectrum of colors reflected from the surface. Using an atomic force microscope images from red and green porous silicon samples are collected. In this paper we relate the optical color of the surface to the size of scattering features on the textured surface. From image segmentation using the watershed transform the height distributions of the optical scattering features are determined. The heights of these surface features are then used as input variables to a computer simulation of a reflective grating. The computer predicted color is compared to the measured color. In this manner, by inspection of the reflected color from the textured porous silicon surface the physical size of the surface features can be estimated.