摘要:

Tellurium samples in which current flowed parallel to thecaxis were irradiated at 78°K with 20‐Mev electrons. The conductivity increased linearly with a slope of 1.0×10−14(ohm‐cm)−1per electron/cm2up to at least 3×1014electrons/cm2. Beyond 3×1015electrons/cm2the slope was approximately one tenth of the initial value. The reciprocal of the Hall coefficient decreased at first and then increased. Between 1×1013and 5×1013electrons/cm21/RHincreases linearly from 3×10−5to 6.3×10−5coulomb/cm3. After irradiation, the samples showed no measurable conductivity changes during 14 hr at 78°K. After a day's anneal at 300°K the 78°K conductivity returned to its preirradiation value.N‐type germanium was irradiated with 20‐Mev electrons at room temperature. Conductivity measurements indicated that the sample became intrinsic and thenptype. However, the detailed dependence of conductivity on radiation dosage did not agree with a calculation based on four energy levels introduced into the gap. Carrier lifetime changes were also observed.

ISSN:0021-8979    

DOI:10.1063/1.1735299

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The effects of high‐energy radiation on the electrical properties of compound semiconductors are reviewed. Emphasis is placed on those effects which can be interpreted in terms of energy levels. The following compounds are discussed: InSb, InAs, GaSb, AlSb, GaAs, InP, CdTe, and SiC. The implications of bombardment‐produced changes in carrier concentration on possible energy levels are considered. Of the compound semiconductors, only InSb, irradiated at 200°K with electrons, has been sufficiently studied to enable a determination of the positions of the energy levels and their rates of generation. The annealing behavior of both InSb and GaSb is complex. A possible interpretation of these annealing characteristics in terms of shifting energy levels is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735300

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

A brief review is given of the present status of precipitation phenomena in semiconductors. Recent theoretical advances in the analysis of diffusion‐limited precipitation are described. The precipitation of Li and Si is discussed as an example of diffusion‐limited precipitation in which metastable centers are observed, and the precipitation of Cu as an example to which formal nucleation theory appears to apply. A recent theory of the clustering of oxygen in Si is described and its significance in terms of the nucleation process is indicated. It is emphasized that a number of techniques are now available for the observation of tiny aggregates of impurities in semiconductors, and the need for a consistently microscopic theory of nucleation is pointed out.

ISSN:0021-8979    

DOI:10.1063/1.1735301

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Important information concerning atomic models of the defects in damaged crystals can be obtained from measurements of bulk length changes, &Dgr;L/L, and x‐ray lattice parameter changes, &Dgr;a/a, during irradiation and subsequent recovery. These quantities are not necessarily equal, and their magnitudes and signs may serve to discriminate between possible models. A detailed description of the &Dgr;L/Land &Dgr;a/aeffects to be expected from models consisting of point imperfections (either uniformly distributed or clustered), displacement spike regions, and dislocation loops is given. Additional discussion is given of the effects expected in measurements of low‐angle x‐ray scattering, Laue‐Bragg reflection broadening, Laue‐Bragg reflection intensities, and x‐ray diffuse scattering. The currently available experimental results on irradiated germanium are discussed in an attempt to discriminate between the various models. Comparatively simple models consisting of clusters of vacancies and clusters of interstitials are probably consistent with present experiment. No information is available regarding the shapes of these regions. More complicated models are not excluded, of course. The aforementioned techniques are compared with electrical measurements in semiconductors, and some of the strengths and weaknesses of the various methods are assessed. The need for further measurements of all types is emphasized.

ISSN:0021-8979    

DOI:10.1063/1.1735302

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Radiation induced defects studied through changes in conductivity and Hall coefficient have been observed to anneal in a number of different temperature ranges. Only those processes occurring above 80°K and involving defects created by electron irradiation have been considered in this paper. It has been found that the first annealing process inn‐type germanium occurs at about 50°C and is structure sensitive, apparently to the original chemical donor impurity. Higher temperature annealing processes, observed at about 200°C and previously interpreted as due to direct annihilation of vacancies and interstitials must also be sensitive to other crystal defects. Inp‐type germanium there is a process of rearrangement of a defect center at about 200°K, exhibiting first order kinetics, but with a time constant which is strongly dependent upon the charge state of the defect. At about 120°C the defects inptype apparently anneal out completely, in striking contrast to then‐type case. Less extensive silicon measurements, showing lifetime recovery between 200 and 400°C again indicate through their kinetics the importance of other impurities or defects in the annealing process.

ISSN:0021-8979    

DOI:10.1063/1.1735303

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Irradiation at ∼10°K using 1.10 Mev electrons produces very different changes in the electrical properties ofn‐type Ge as compared to those produced inp‐type Ge. Inn‐type Ge, more carriers are removed per incident electron at 10°K than at 78°K. However about 50% of the removed carriers are recovered in two stages of annealing, at 34°K and 64°K, after low temperature irradiation. Irradiation at 0.315 Mev, after a 1.10 Mev irradiation, also produces recovery of about 50% of the carriers removed by the 1.10 Mev irradiation. Inp‐type Ge, low temperature irradiation is at least 100 times less effective in removing carriers than is the case inntype. Annealing of an irradiatedp‐type sample to 130°K produces no measurable change. It is concluded that the stability of close‐vacancy‐interstitial pairs against recombination is less inptype than inn‐type Ge. A qualitative argument as to the origin of this difference in stability is presented.

ISSN:0021-8979    

DOI:10.1063/1.1735304

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The various mechanisms producing damping of ultrasonic elastic waves in solids are reviewed in this paper. Particular attention is given to the changes in attenuation produced by pinning of dislocation lines. Measurements of ultrasonic attenuation in irradiated single crystals of NaCl are presented and discussed, on the assumption that the dislocation density remains constant while the radiation displaced defects pin the dislocations. The effects on the velocity of propagation are discussed on the basis of the same model.

ISSN:0021-8979    

DOI:10.1063/1.1735305

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Electron microscope and electron diffraction studies on the surfaces of CP‐4 etched germanium specimens have shown that the changes in etching behavior induced by fast neutron irradiation occur as a result of a gross change in chemical behavior and cannot be due to local variations in the etching rate in the vicinity of the structural defects introduced by the irradiation. Observations on network structures which are produced under certain conditions of etching indicate that these arise as a result of mechanical preparation of the surfaces or from changes in the etching process and are apparently unrelated to any prior substructure in the material.

ISSN:0021-8979    

DOI:10.1063/1.1735306

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Cross sections for the displacement of lattice atoms by gamma rays for energies up to 5 Mev have been calculated. The principal contribution is found to come from the Compton effect, in which the atoms are displaced by electrons produced by the incident gamma rays. The calculations have been based on the assumption of a sharp threshold energy for displacement, but cross sections have been computed as a function of the assumed threshold energy. Thus, from the present work it is relatively easy to obtain cross sections based upon other displacement functions.

ISSN:0021-8979    

DOI:10.1063/1.1735307

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The paper reviews the current status of displacement threshold determinations, both theoretical and experimental, in semiconductors. The work of Seitz, Kohn, Klontz, Loferski, and Rappaport, Vavilov,et al., and Brown and Augustyniak on germanium are discussed and compared. Measurements of thresholds in Si and InSb also are discussed briefly.

ISSN:0021-8979    

DOI:10.1063/1.1735308

出版商:AIP    

年代:1959

数据来源: AIP