GaAs Compound Semiconductors Research Articles

A generalized mathematical modeling and performance analysis of GaAs, m-Si and Ge single - junction solar PV cells

Earlier theoretical approaches have analyzed the performance of semiconductor materials for the influence of temperature and band gap which is implemented in solar photovoltaic systems. This paper investigates the detailed mathematical analysis of single junction semiconductor materials such as Gallium Arsenide (GaAs), mono-crystalline Silicon (m-Si) and Germanium (Ge) solar cells parameters namely, Band gap (Eg), reverse saturation current (Io), shunt resistance (Rsh), Short circuit current (Isc), open circuit voltage (Voc), Fill factor (FF), Maximum Power (Pmax) and Efficiency (Ƞ) for temperature ranging from 273K (≈0°C) to 373K (≈100°C). The optimized cell parameters values are obtained under Air Mass 1.5 Global spectrum (Area = 100cm2 and Irradiance = 100 mW/cm2 for the semiconductor materials (GaAs, m-Si and Ge)) at 300K (≈25°C) are compared to identify the higher efficiency and open circuit voltage. Among the semiconductor materials, the single junction GaAs compound semiconductor material is identified with better efficiency and optimized open circuit voltage. A generalized mathematical model of semiconductor materials is developed using single diode equivalent circuit model under SIMULINK platform and it is used to observe the effect of different temperature, irradiance levels, series resistance and shunt resistance values on the performance of solar cells. The discussion is extended for a 2KW PV array for the semiconductor materials (GaAs, m-Si and Ge) under different temperature and irradiance levels. Evaluating the performance of a PV array, rather than individual cells, provides a more comprehensive understanding of how the chosen semiconductor materials function as part of a larger solar energy system.

Evaporating and Sputtering of High-Density Ag Nanotwinned Films on GaAs Compound Semiconductor Wafers

Evaporating and Sputtering of High-Density Ag Nanotwinned Films on GaAs Compound Semiconductor Wafers

Accurate measurement of electric potentials in biased GaAs compound semiconductors by phase-shifting electron holography.

The innate electric potentials in biased p- and n-type GaAs compound semiconductors and the built-in potential were successfully measured with high accuracy and precision by applying in situ phase-shifting electron holography to a wedge-shaped GaAs specimen. A cryo-focused-ion-beam system was used to prepare the 35°-wedge-shaped specimen with smooth surfaces for a precise measurement. The specimen was biased in a transmission electron microscope, and holograms with high-contrast interference fringes were recorded for the phase-shifting method. A clear phase image around the p-n junction was reconstructed even in a thick region (thickness of ~700 nm) at a spatial resolution of 1 nm and precision of 0.01 rad. The innate electric potentials of the unbiased p- and n-type layers were measured to be 12.96 ± 0.17 V and 14.43 ± 0.19 V, respectively. The built-in potential was determined to be 1.48 ± 0.02 V. In addition, the in situ biasing measurement revealed that the measured electric-potential difference between the p and n regions changed by an amount equal to the voltage applied to the specimen, which indicates that all of the external voltage was applied to the p-n junction and that no voltage loss occurred at the other regions.

52‐3: Invited Paper: Combining Engineered EPI Growth Substrate Materials with Novel Test and Mass‐Transfer Equipment to Enable MicroLED Mass‐Production

Advances in layer‐transfer methods are making large‐area growth templates a reality for GaN and GaAs compound semiconductors. QMAT will introduce its layer‐transfer technology tuned for microLED applications integrating functional layers that simplify printability and testability. MicroLED yield and test challenges will also be discussed.

9.1: Invited Paper: Materials, Process and Production Equipment Considerations to Achieve High‐Yield MicroLED Mass‐Production

Advances in layer‐transfer methods are making large‐area growth templates a reality for GaN and GaAs compound semiconductors. QMAT will introduce its layer‐transfer technology tuned for microLED applications integrating functional layers that simplify printability and testability. MicroLED yield and test challenges will also be discussed.

PyCDT: A Python toolkit for modeling point defects in semiconductors and insulators

Point defects have a strong impact on the performance of semiconductor and insulator materials used in technological applications, spanning microelectronics to energy conversion and storage. The nature of the dominant defect types, how they vary with processing conditions, and their impact on materials properties are central aspects that determine the performance of a material in a certain application. This information is, however, difficult to access directly from experimental measurements. Consequently, computational methods, based on electronic density functional theory (DFT), have found widespread use in the calculation of point-defect properties. Here we have developed the Python Charged Defect Toolkit (PyCDT) to expedite the setup and post-processing of defect calculations with widely used DFT software. PyCDT has a user-friendly command-line interface and provides a direct interface with the Materials Project database. This allows for setting up many charged defect calculations for any material of interest, as well as post-processing and applying state-of-the-art electrostatic correction terms. Our paper serves as a documentation for PyCDT, and demonstrates its use in an application to the well-studied GaAs compound semiconductor. We anticipate that the PyCDT code will be useful as a framework for undertaking readily reproducible calculations of charged point-defect properties, and that it will provide a foundation for automated, high-throughput calculations. Program summaryProgram title: PyCDTProgram Files doi:http://dx.doi.org/10.17632/7vzk5gxzh3.1Licensing Provisions: MIT License.Programming language: PythonExternal routines/libraries: NumPy [1], matplotlib [2], and Pymatgen [3],Nature of problem: Computing the formation energies and stable point defects with finite size supercell error corrections for charged defects in semiconductors and insulators.Solution method: Automated setup, and parsing of defect calculations, combined with local use of finite size supercell corrections. All combined into a code with a standard user-friendly command line interface that leverages a core set of tools with a wide range of applicability.Additional comments: This article describes version 1.0.0. Program obtainable from https://bitbucket.org/mbkumar/pycdt

Analysis of GaAs Compound Semiconductors and the Semiconductor Laser Diode using Off-Axis Electron Holography, Lorentz Microscopy, Electron Diffraction Microscopy and Differential Phase Contrast STEM

Analysis of GaAs Compound Semiconductors and the Semiconductor Laser Diode using Off-Axis Electron Holography, Lorentz Microscopy, Electron Diffraction Microscopy and Differential Phase Contrast STEM

Imaging of built-in electric field at a p-n junction by scanning transmission electron microscopy.

Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.

Terahertz Switch Based on Waveguide-Cavity-Waveguide Comprising Cylindrical Spoof Surface Plasmon Polariton

This paper demonstrates a terahertz (THz) switch that comprises a metallic perfect conductor in the form of periodically corrugated cylindrical waveguides surrounding a dielectric medium consisting of GaAs compound semiconductor. The proposed switch deploys a composite waveguide-cavity-waveguide structure. The switch controls its state by dynamically altering the optical properties of an engineered nonlinear material inside the cavity, while the corrugated waveguides on both sides of the cavity are incorporated to limit the propagation of electromagnetic (EM) waves at nearly THz frequencies only. At the resonant frequency, the corrugated waveguide allows strong EM confinement inside the grooves. The cavity has been designed to achieve a high quality factor as well as to trap EM waves for a significant period of time. Small changes in the GaAs refractive index inside the grooves can alter the cavity resonant frequency. Localized doping near the metal conductor inside the cavity is implemented so that by applying a voltage between the metal electrode and the depletion region in the dielectric medium, the switch can be altered from the ON state to the OFF state, and vice versa.

Direct observation of dopant distribution in GaAs compound semiconductors using phase-shifting electron holography and Lorentz microscopy

Phase-shifting electron holography and Lorentz microscopy were used to map dopant distributions in GaAs compound semiconductors with step-like dopant concentration. Transmission electron microscope specimens were prepared using a triple beam focused ion beam (FIB) system, which combines a Ga ion beam, a scanning electron microscope, and an Ar ion beam to remove the FIB damaged layers. The p-n junctions were clearly observed in both under-focused and over-focused Lorentz microscopy images. A phase image was obtained by using a phase-shifting reconstruction method to simultaneously achieve high sensitivity and high spatial resolution. Differences in dopant concentrations between 1 × 10(19) cm(-3) and 1 × 10(18) cm(-3) regions were clearly observed by using phase-shifting electron holography. We also interpreted phase profiles quantitatively by considering inactive layers induced by ion implantation during the FIB process. The thickness of an inactive layer at different dopant concentration area can be measured from the phase image.

Development of advanced electron holographic techniques and application to industrial materials and devices

The development of a transmission electron microscope equipped with a field emission gun paved the way for electron holography to be put to practical use in various fields. In this paper, we review three advanced electron holography techniques: on-line real-time electron holography, three-dimensional (3D) tomographic holography and phase-shifting electron holography, which are becoming important techniques for materials science and device engineering. We also describe some applications of electron holography to the analysis of industrial materials and devices: GaAs compound semiconductors, solid oxide fuel cells and all-solid-state lithium ion batteries.

Quantum confinement effects on the band structure and dielectric properties of nanostructured GaAs

The electronic band structure and dielectric properties of a GaAs quantum well have been investigated using the pseudopotential approach. The effect of quantum confinement on the electronic and dielectric properties of GaAs has been examined. It is found that significant variations in the studied properties occur at quantum well widths below 5 nm. The information may be useful in obtaining derived electronic and dielectric properties, which was not possible in the unconfined (bulk) GaAs compound semiconductor.

Room-temperature self-annealing of heavy-ion-irradiated InGaAs/GaAs quantum wells

The long-term stability of defects with the ageing of heavy-ionirradiated and post-irradiated-annealed InGaAs=GaAs compound semiconductor quantum wells is reported using the time-resolved upconversion technique of luminescence lifetimes. The defects created by Ni þ -heavy-ion irradiation are found to be thermally unstable. The ageing tests prove that a substantial amount of defects are removed by self-annealing in about a month of time even at room temperature through a slow diffusion process, resulting in a dynamically stable sample but with a twofold increment in lifetimes. If the sample is annealed upon Ni þ irradiation, the defects are removed immediately, yielding stable and much longer relaxation times independent of the ageing process. These results may be useful in designing devices with an active region as ion-irradiated semiconductor quantum wells.

Transmission electron microscopy investigation of the Ar+ ion irradiation effect in semiconductor GaAs

Room temperature irradiation effect of GaAs compound semiconductor by 100 keV Ar+ ions has been systematically studied by means of transmission electron microscopy. The dose dependenceoof the Ar+ ion irradiation and room temperature annealing effects have been investigated. The experimental results show that the structure of GaAs transforms from perfect crystalline through weakly and severely damaged crystalline to amorphous states with the increase of the irradiation dose and the damaged states are changed during room temperature annealing.

Recent Progress of Alloyed Ohmic Contacts to GaAs Compound Semiconductors

ABSTRACTLow resistance, alloyed AuGeNi Ohmic contacts have been extensively used in the current manufacturing GaAs devices. However, extension of usage of these devices to Very Large Scale Integration levels requires the contacts with excellent thermal stability, shallow diffusion depth, and smooth contact surface in addition to low contact resistance. In the present paper recent studies for development of “non-gold” Ohmic contacts which improve the poor contact properties of the alloyed Ohmic contacts are rev i ewed.

Boron Nitride Thin Insulating Films on GaAs Compound Semiconductors

Boron Nitride Thin Insulating Films on GaAs Compound Semiconductors