Comparative Evaluation of the Polar Organic Chemical Integrative Sampler in Two Types of Validation Systems Simulating Peak Concentration Events

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

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Structural and electronic properties of defects in semiconductors

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136398 ◽

1995 ◽

Vol 53 ◽

pp. 4-5

Author(s):

J.L. Batstone

Keyword(s):

Semiconductor Device ◽

Chemical Vapor ◽

Misfit Strain ◽

Organic Chemical ◽

Extended Defects ◽

Transmission Electron ◽

Semiconductor Thin Films ◽

Wide Range ◽

Metal Organic ◽

Film Substrate

The development of growth techniques such as metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy during the last fifteen years has resulted in the growth of high quality epitaxial semiconductor thin films for the semiconductor device industry. The III-V and II-VI semiconductors exhibit a wide range of fundamental band gap energies, enabling the fabrication of sophisticated optoelectronic devices such as lasers and electroluminescent displays. However, the radiative efficiency of such devices is strongly affected by the presence of optically and electrically active defects within the epitaxial layer; thus an understanding of factors influencing the defect densities is required.Extended defects such as dislocations, twins, stacking faults and grain boundaries can occur during epitaxial growth to relieve the misfit strain that builds up. Such defects can nucleate either at surfaces or thin film/substrate interfaces and the growth and nucleation events can be determined by in situ transmission electron microscopy (TEM).

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{10} edge dislocations in YSZ films grown on (100)MgO by PLD

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170384 ◽

1994 ◽

Vol 52 ◽

pp. 530-531

Author(s):

Jason R. Heffelfinger ◽

C. Barry Carter

Keyword(s):

Thin Films ◽

Semiconductor Lasers ◽

Vapor Deposition ◽

Substrate Surface ◽

Laser System ◽

Average Energy ◽

Target Material ◽

Chemical Vapor ◽

Buffer Layers ◽

Organic Chemical

Yttria-stabilized zirconia (YSZ) is currently used in a variety of applications including oxygen sensors, fuel cells, coatings for semiconductor lasers, and buffer layers for high-temperature superconducting films. Thin films of YSZ have been grown by metal-organic chemical vapor deposition, electrochemical vapor deposition, pulse-laser deposition (PLD), electron-beam evaporation, and sputtering. In this investigation, PLD was used to grow thin films of YSZ on (100) MgO substrates. This system proves to be an interesting example of relationships between interfaces and extrinsic dislocations in thin films of YSZ.In this experiment, a freshly cleaved (100) MgO substrate surface was prepared for deposition by cleaving a lmm-thick slice from a single-crystal MgO cube. The YSZ target material which contained 10mol% yttria was prepared from powders and sintered to 85% of theoretical density. The laser system used for the depositions was a Lambda Physik 210i excimer laser operating with KrF (λ=248nm, 1Hz repetition rate, average energy per pulse of 100mJ).

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Characterisation of multilayer materials using a position-sensitive atom probe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176253 ◽

1990 ◽

Vol 48 (4) ◽

pp. 624-625

Author(s):

RAD Mackenzie ◽

G D W Smith ◽

A. Cerezo ◽

J A Liddle ◽

CRM Grovenor ◽

...

Keyword(s):

Quantum Well ◽

Quantum Wells ◽

Spatial Information ◽

Chemical Vapour ◽

Atom Probe ◽

Organic Chemical ◽

Growth Stages ◽

Multiple Quantum ◽

Quartz Wool ◽

Position Sensitive

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.

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TEM study of very thin InGaAsP layers grown by liquid-phase epitaxy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100176496 ◽

1990 ◽

Vol 48 (4) ◽

pp. 672-673

Author(s):

N.A. Bert ◽

A.O. Kosogov

Keyword(s):

Liquid Phase ◽

Liquid Phase Epitaxy ◽

Chemical Vapor ◽

Growth Conditions ◽

Dark Field ◽

Organic Chemical ◽

Simple Liquid ◽

Cross Sectional ◽

Conventional Procedure ◽

Double Heterostructures

The very thin (<100 Å) InGaAsP layers were grown not only by molecular beam epitaxy and metal-organic chemical vapor deposition but recently also by simple liquid phase epitaxy (LPE) technique. Characterization of their thickness, interfase abruptness and lattice defects is important and requires TEM methods to be used.The samples were InGaAsP/InGaP double heterostructures grown on (111)A GaAs substrate. The exact growth conditions are described in Ref.1. The salient points are that the quarternary layers were being grown at 750°C during a fast movement of substrate and a convection caused in the melt by that movement was eliminated. TEM cross-section specimens were prepared by means of conventional procedure. The studies were conducted in EM 420T and JEM 4000EX instruments.The (200) dark-field cross-sectional imaging is the most appropriate TEM technique to distinguish between individual layers in 111-v semiconductor heterostructures.

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Comparison of In-the-Ear and Over-the-Ear Hearing Aid Fittings

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.5104.362 ◽

1986 ◽

Vol 51 (4) ◽

pp. 362-369 ◽

Cited By ~ 4

Author(s):

Donna M. Risberg ◽

Robyn M. Cox

Keyword(s):

Hearing Aids ◽

High Frequency ◽

Comparative Evaluation ◽

Speech Intelligibility ◽

Hearing Aid ◽

Hearing Aid Fitting ◽

The Difference ◽

Functional Gain ◽

The Relationship

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

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