摘要:

This paper reviews applications of cathodoluminescence scanning electron microscopy in the assessment of optical and electronic properties of semiconductors. The assessment includes, for example, information on band structure and impurity levels derived from spectroscopic cathodoluminescence, analysis of dopant concentrations at a level which is in some cases several orders of magnitude better than x‐ray microanalysis, and mapping of carrier lifetimes and defects. Recent advances in both the various cathodoluminescence techniques and the processes leading to electron‐beam‐induced luminescence in semiconductors are reviewed. Possible future trends are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.336491

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Measurements were made at the gold and silver freezing points to demonstrate the accuracy of the new optical fiber thermometer (OFT). It is shown that the output signal from the OFT is related to the radiance from a blackbody source in a simple manner and that the temperature interval between the gold and silver freezing points, as determined with the OFT, is close to other recent results.

ISSN:0021-8979    

DOI:10.1063/1.336533

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An x‐ray imaging technique has been studied for the purpose of observing the current density profile in a high‐current relativistic electron beam (50 MeV, 10 kA). Calculations and measurements of energy spectra and intensities are in good agreement. Results indicate sufficient photon yield for pinhole imaging when the beam deposits a small part of its energy in high‐Zgas or a thin high‐Zfoil. CharacteristicLandKx‐ray emission is not found not be a reliable technique due to strongLandKshell fluorescence in the presence of intense bremsstrahlung radiation. It is also found that at pressures on the order of one atmosphere, the density of energy deposition in a gas cell is too small to generate sufficient photon yield for time‐resolved measurements.

ISSN:0021-8979    

DOI:10.1063/1.336534

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The effect of a nonuniformly emitting cathode on a space‐charge‐limited diode is analyzed. The first part of the analysis is a calculation of the extent to which inhomogeneities in the space charge are reduced by the motion of electrons in directions parallel to the cathode surface. It was found that, in typical cases, outside of a small layer adjacent to the cathode, the space‐charge density is virtually constant on surfaces parallel to the cathode. Because of this the total diode current was found to be given by Child’s law even when the cathode has patches whose emission is saturated.

ISSN:0021-8979    

DOI:10.1063/1.336535

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Large optical‐cavity GaAs/GaAlAs double‐heterostructure stripe geometry laser with laterally effective step change of the refractive index is described. The stabilization of the transverse mode is achieved by regrowing an embedded stripe selectively on a large optical cavity, using metallo‐organic chemical vapor deposition. The near‐field and the far‐field patterns confirm the index guiding mechanism of the light. No kinks were observed in the light versus current characteristics up to light power of 200 mW/facet. The threshold current uniformity is comparable to those of gain‐guided lasers grown by metallo‐organic chemical vapor deposition.

ISSN:0021-8979    

DOI:10.1063/1.336536

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Correlations between degradation and device characteristics are investigated in InGaAsP/InP buried heterostructure lasers. The logarithm of threshold‐current increase rates is confirmed to be proportional to the voltage decrease at low current when injected carrier lifetime decreases during aging. When leakage current increases during aging, devices having a low initial voltage also tend to degrade to a large extent. These correlations hold within an operating range limited by the device structure and the material used during fabrication.

ISSN:0021-8979    

DOI:10.1063/1.336537

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

It is shown that the well‐known damped relaxation oscillation resonance in the small signal equations for the dynamic photon and carrier densities becomes more highly damped when the photon density is axially inhomogeneous. An antireflective coating withR=0.02 on one laser facet reduced the resonance in the light output from a 1.3‐&mgr;m Vee‐groove laser yielding a flat response with a 3‐dB bandwidth of 5 GHz. We also show that the wavelength modulation or chirp, due to the carrier‐dependent contribution of the refractive index, is largely eliminated.

ISSN:0021-8979    

DOI:10.1063/1.336538

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The analysis for the calculation of the transport coefficients of a chemically reacting partially ionized gas in the presence of a magnetic field is presented here. Taking the phenomenological kinetic equations and considering the ionization and recombination processes only due to electron impact parameter, the Chapman–Enskog method is used to obtain these transport coefficients. Sample numerical calculations are made for the transport coefficients of a potassium‐seeded argon gas.

ISSN:0021-8979    

DOI:10.1063/1.336539

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A previous paper presented numerically determined values of a dimensionless quantity which is useful for characterizing gas discharge columns with electron production and loss rates linear and quadratic in electron density. That quantity, denoted byS, is useful for calculating voltage‐current characteristics and for indicating the shape of the electron density distribution, i.e., its degree of diffuseness or constriction. (In terms of the electron densityne,Sis the integral of −∇2ne/neover the column cross section.) Crawford has presented an analytic approximation for a limited range ofSfor the case of a circular column cross section. In this note Crawford’s expression is compared with values obtained numerically, and it is found to be a very good approximation over its limited range of applicability. In addition, modified versions of Crawford’s expression are provided for use with all possible relative magnitudes and combinations of signs of the linear and quadratic rates. Analytic relationships between the maximum electron density and average electron density are also provided, both for direct use and to facilitate use of the expressions forS.

ISSN:0021-8979    

DOI:10.1063/1.336540

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Time‐resolved voltage, current and optical emission from Cl, Cl+, Cl+2, and small amounts of added Ar were studied in 0.3 Torr chlorine discharges at 13.2 MHz and 220 kHz, above and below the ion transit frequency (ITF). Emissions, measured as a function of position, were deconvoluted to correct for the finite fluorescence lifetimes and extract the electron impact excitation rates. At 220 kHz, emission falls to zero at the voltage zero point crossings due to electron energy relaxation and attachment. Emission and excitation in a sheath peak sharply about 70 ns before electrode voltage reaches its positive maximum and are stimulated by electron current. Emission then falls to zero and reaches a second maximum ∼300 ns after the electrode voltage reaches its negative peak. This emission is excited by a secondary electron avalanche from ions crossing the sheath. Excitation maxima in the center of the discharge lag the voltage peaks by ∼25°. Analyses of time and spatially resolved ratios of emission from Cl and Ar show that actinometric techniques can give an erroneous measure of atom concentrations unless the viewing area and phase are taken into account. At 13.2 MHz, ions cannot respond to the time‐varying fields, and excitation in the sheath peaks in phase with the anodic part of the cycle with minimal excitation during the cathodic phase. Emission from Cl+was not observable. The lack of high‐energy ion bombardment drastically reduces secondary emission and excitation in the cathodic sheath. In the center of the discharge, excitation peaks twice per cycle, but unlike the low‐frequency case, it does not fall to zero. The electron energy relaxation frequency (&ngr;u) is estimated to be 64 MHz.

ISSN:0021-8979    

DOI:10.1063/1.336541

出版商:AIP    

年代:1986

数据来源: AIP