摘要:

A large active‐area avalanche photodiode is described. The use of the ``reach through shortly before breakdown'' concept for achieving high stable electric fields in conjunction with a metal‐oxide‐semiconductor structure allows stable device operation for active areas up to 5 cm2.

ISSN:0021-8979    

DOI:10.1063/1.1662252

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A high‐purity GaAs sample with a measured room‐temperature mobility of 15 200 cm2/V sec is examined in detail. Resistivity and Hall measurements are in reasonable agreement with a previously developed model which shows that conducting inhomogeneities can result in anomalously high measured mobilities. A sizeable number of precipitates (probably gallium) are observed in the sample.

ISSN:0021-8979    

DOI:10.1063/1.1662253

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

High‐energy electrons (≈7 MeV) were used to radiation dope extrinsic silicon. Bothn‐ andp‐type silicon photodetectors were fabricated using this doping technique. The 500°K blackbody responsivity, spectral response, and peak detectivity were determined for these devices. The peak detectivity values measured were 4.8×1011cm Hz1/2W−1at 2.15 &mgr; for 0.1‐&OHgr; cmn‐type devices and 3.7×1011cm Hz1/2W−1at 40 &mgr; for 10‐&OHgr; cmp‐type detectors. A comparison of the thermally generated background majority carrier concentration for radiation‐doped and conventional impurity‐doped detectors is made.

ISSN:0021-8979    

DOI:10.1063/1.1662254

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

It has been established, by electrical and electron‐optical studies, that the oxide surface layer is responsible for the particularly stable properties of stainless steel when used for high‐voltage electrodes. The growth of this surface oxide has been studied ellipsometrically. After cleaning the surface by electron bombardment the growth of the layer was monitored in the pressure range 10−8Torr‐atmospheric pressure, and the temperature range 300–1300°K. The equilibrium thickness at room temperature and at atmospheric pressure is [inverted lazy s]30 Å. A temperature in excess of 1000°C is required to remove the film at 10−8Torr.

ISSN:0021-8979    

DOI:10.1063/1.1662255

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The MOS Hall technique has been used to measure the temperature dependence of the average electron and hole mobilities at various depths into the film. Electron and hole concentrations were also determined as a function of temperature and distance from the film surface. It has been found that a second ionization level, in addition to the intentionally introduced arsenic impurity, exists in then‐type films at approximately 0.1 eV below the conduction band. This level has been associated with theSiO4+complex known to be present in oxygen‐rich silicon. The density of this added impurity increases with depth into the film and has, therefore, been associated with the mobility gradient. The effect of this complex on the temperature dependence of the mobility is examined and the appearance of a temperature‐independent neutral impurity scattering mechanism is evident. Neutral impurities inp‐type films also are suggested to explain the hole‐mobility‐vs‐temperature data and they may be related to theB‐SiO4+molecule known to exist in oxygen‐rich boron‐doped silicon. The effect of stress on the mobility has been suggested as a possible cause for the reduction in electron and hole mobilities at elevated temperatures where phonon scattering appears dominant.

ISSN:0021-8979    

DOI:10.1063/1.1662256

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Fast electrons in solids lose energy primarily to plasmons which subsequently decay into an electron‐hole pair. The electron and hole may create additional electron‐hole pairs if they have sufficient energy. The average energy to create an electron‐hole pair,Ex, is thus given essentially by ℏ &ohgr;p/n, where ℏ &ohgr;pis the plasmon energy andnis the number of pairs which are created by the plasmon and its decay products. The values ofnand henceExdepend on the ratio ℏ&ohgr;p/Eg, whereEgis the usual band gap in semiconductors and insulators. We have found that for a simple model of direct and indirect materials, sharp thresholds exist for various values ofn. For direct‐gap materials,n=1 for 1< ℏ&ohgr;p/Eg<4,n=3 for 4< ℏ&ohgr;p/Eg<12, etc. Similar relations for indirect‐gap materials have also been obtained. Consideration of phonon losses, effective masses, and problems withkconservation indicate that the changes innvs ℏ&ohgr;p/Egshould be smoothed for real materials. but not eliminated. Our theoretical values forEx/Egallow values lower than previous treatments and give good agreement with known experimental values. Some problems associated with determining the theoretical value of &ohgr;pfor materials withdelectrons are discussed. Some experiments for testing the theory are suggested. The importance ofExin determining the efficiency of phosphors is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1662257

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

This paper is concerned with the evaluation of the optical properties of the portion of a beam of charged particles lying in the plane of symmetry of any toroidal condenser used as an electrostatic mirror. It gives a general treatment that permits the calculation of the optical characteristics and the aberrations when a trajectory and its derivatives relative to the entry energy and angle are known. Results are applied to the case of a cylindrical condenser, resulting in an important extension of the knowledge of its properties. No attention is given to space‐charge effects and to the motion off the plane symmetry where the electric field is generally not central anymore.

ISSN:0021-8979    

DOI:10.1063/1.1662258

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Here new periodic structures are proposed for distributed lasers, utilizing the thickness variation introduced in a multilayer thin‐film optical waveguide. Wave propagation in such structures is analyzed. Expressions are derived for the amount of distributed feedback and possible scattering losses. From the coupled‐wave equations, the laser‐oscillation conditions are set up. Computational results for the GaAs&sngbnd;GaxAl1−xAs and dye lasers are presented. The applicability of the proposed scheme for distributed feedback to semiconductor, dye, and solid‐state lasers is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1662259

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

In this paper, we report the first laser‐excited optical double‐resonance experiments in rare‐earth‐doped crystals. Infrared upconversion in LaCl3: Pr3+and LaF3: Pr3+has been achieved by means of a tunable cw dye laser pump. The quantum efficiency of the upconversion process at 2.03 &mgr; in LaCl3: Pr3+is 1.2×10−3, which is an improvement of 4×105over the highest efficiency found previously with incoherent sources. It is shown that an efficiency of 1 can be easily obtained with higher fluxes and improved crystal quality. Direct excitation of the output fluorescence from the3P0level is observed in both LaCl3: Pr3+and LaF3: Pr3+when the dye laser frequency is resonant with the states of the lower‐lying1D2manifold in the absence of the infrared input. Detailed assignments of the observed double‐resonance transitions have been made from wavelength and polarization measurements.

ISSN:0021-8979    

DOI:10.1063/1.1662260

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Theoretical studies are made of the effects of pressure on candidate materials for use as windows in high‐power infrared laser systems. When the window in a laser system is subjected to a uniform static pressure, the resulting deformation can distort the laser beam or fracture the window. Two aspects of this problem are considered:pressure‐induced optical distortion and the effect of including pressure in previously calculated figures of merit forthermally‐induced optical distortion. An expression for the window thickness required to prevent pressure‐induced optical distortion from halving the target intensity is derived, and values are tabulated for various materials. Comparing these values with the minimum thickness required to prevent material fracture indicates that the thickness of large‐diameter windows of strong materials is determined by the pressure‐induced optical distortion, whereas the thickness of small‐diameter windows of strong materials is determined by the pressure‐induced fracture. The optical distortion resulting from the static deformation of a window under its own weight is negligible with respect to that from a pressure of 7.3 psi under usual operating conditions. An expression obtained for the strength of a material at which the fracture and pressure‐induced optical‐distortion effects are equally important should be useful in material‐strengthening programs. In previous figures of merit, various materials were compared on the basis of a common fixed value of the window thickness. In many applications, where the window diameter and the pressure have specified values, new figures of merit are required in order to account for the greater thickness required for weaker materials. The new figures of merit, which are simply the values of intensity the window can transmit under specified conditions, change the preference of materials in a number of cases.

ISSN:0021-8979    

DOI:10.1063/1.1662261

出版商:AIP    

年代:1973

数据来源: AIP