Quantitative measurement of the composition of Al_xGa_(1−x)As heterostructures using a simple backscattered electron detector

We describe a technique for the quantitative measurement of composition in Al_xGa_(1−x)As heterostructures using a simple solid‐state backscattered electron detector in a scanning electron microscope. Calibration data are presented and are shown to be consistent with the Castaing [Adv. Electron. Electron Phys. 13, 317 (1960)] theory. The technique is applied to image representative Al_xGa_(1−x)As heterostructures including a graded index separate confinement heterostructure (GRINSCH) laser structure

Application of selective epitaxy to fabrication of nanometer scale wire and dot structures

The selective growth of nanometer scale GaAs wire and dot structures using metalorganic vapor phase epitaxy is demonstrated. Spectrally resolved cathodoluminescence images as well as spectra from single dots and wires are presented. A blue shifting of the GaAs peak is observed as the size scale of the wires and dots decreases

Nanometer scale wire structures fabricated by diffusion-induced selective disordering of a GaAs(AlGaAs) quantum well

A shallow zinc diffusion technique is used to selectively disorder a GaAs quantum well creating nanometer scale wire structures. Spectrally resolved cathodoluminescence images of the structures are presented as well as local spectra of cathodoluminescence emission from the structures. Blue shifting of the luminescence from the wire structures is observed

Facet modulation selective epitaxy–a technique for quantum-well wire doublet fabrication

The technique of facet modulation selective epitaxy and its application to quantum-well wire doublet fabrication are described. Successful fabrication of wire doublets in the AlxGa1–xAs material system is achieved. The smallest wire fabricated has a crescent cross section less than 140 Å thick and less than 1400 Å wide. Backscattered electron images, transmission electron micrographs, cathodoluminescence spectra, and spectrally resolved cathodoluminescence images of the wire doublets are presented

A novel technique for the direct determination of carrier diffusion lengths in GaAs/AlGaAs heterostructures using cathodoluminescence

A new technique for determining carrier diffusion lengths in direct gap semiconductors by cathodoluminescence measurement is presented. Ambipolar diffusion lengths are determined for GaAs quantum well material, bulk GaAs, and Al_xGa_(1-x)As with x up to 0.38. A large increase in the diffusion length is found as x approaches 0.38 and is attributed to an order of magnitude increase in lifetime

Direct determination of the ambipolar diffusion length in GaAs/AlGaAs heterostructures by cathodoluminescence

A new technique for determining carrier diffusion lengths by cathodoluminescence measurements is presented. The technique is extremely accurate and can be applied to a variety of structures. Ambipolar diffusion lengths are determined for GaAs quantum well material, bulk GaAs, Al0.21Ga0.79As, and Al0.37Ga0.63As. A large increase in the diffusion length is found for Al0.37Ga0.63As and is attributed to an order of magnitude increase in lifetime

A Review of Thermal Acoustical and Special Project Requirements Data in Designing a Duct System

The primary foci in designing a duct system is: 1) Delivery of the correct amount of air; 2) Delivery of air at an acceptable temperature with minimum temperature drop; 3) Delivery of air quietly; and, 4) A system which is applicable to the project conditions. The Sheet Metal and Air Conditioning Association (SMACNA) and the Thermal Insulation Manufacturers Association (TIMA), have done considerable testing on air loss and temperature drop on operating HVAC systems. It is important to note that these tests show that air leakage through unsealed joints is the most significant factor in heat loss. No amount of insulation can make up for a 24 percent air leakage rate in an unsealed, rectangular sheet metal system. Acoustical data is not as readily available. ASHRAE is currently testing acoustical companies; however. this information is not yet available. Based on testing by Owens/Corning Fiberglas, duct attenuation in dB's per lineal foot at 500 HZ of various insulating materials can range from 2.9 dB's t o 3.7 dB's. The last area to consider in designing a duct system is project conditions. This area is not as technically oriented as the other three; however. it is crucial in designing a duct operable system. Items to consider are susceptibility to abuse, concealed or exposed duct, how critical the acoustics are, duct clean out requirements, climate conditions. residential versus commercial construction, and new versus retrofit construction. Without revealing the properties of each system, a failure or a less than acceptable environment for occupants could occur

Effect of Al mole fraction on carrier diffusion lengths and lifetimes in AlxGa1−xAs

The ambipolar diffusion length and carrier lifetime are measured in AlxGa1−xAs for several mole fractions in the interval 0<x<0.38. These parameters are found to have significantly higher values in the higher mole fraction samples. These increases are attributed to occupation of states in the indirect valleys, and supporting calculations are presented

Quantum wire and quantum dot semiconductor lasers

There is currently great interest in fabrication of structures that are two and three dimensional analogs of the conventional quantum well. We review here the physics behind the use of arrays of such lower dimensional structures in semiconductor laser active layers. Methods which are currently under investigation for producing such structures will be discussed