摘要:

The rate of change of minority carrier lifetime in germanium crystals bombarded by 1‐Mev electrons has been studied experimentally as a function of the initial resistivity of the material. Analysis of the data leads to the conclusion that a single recombination center controls lifetime in bothn‐ andp‐type material, that this level is located at either 0.21±0.005 ev from the conduction band or else at 0.26±0.005 ev from the valence band, and that the ratio of the cross section for capture of minority holes is 18 times the cross section for capture of minority electrons. The absolute value of the hole capture cross section is 4.5×10−15cm2if one uses the best available data for the probability of producing a Frenkel defect by a 1‐Mev electron. This large value is compared to the findings of other authors in similar experiments.

ISSN:0021-8979    

DOI:10.1063/1.1735289

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The magnetic susceptibility of semiconductors depends on electronic properties of the lattice, on the motion of free carriers and on the presence of impurity states. Critical points in the work on Ge and Si are reviewed relative to demands they place on theoretical interpretations. Anomalies in the susceptibility of high‐purity specimens, various aspects of valence band carrier susceptibility, and the susceptibility of acceptor states are not as yet explained satisfactorily.

ISSN:0021-8979    

DOI:10.1063/1.1735290

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Magnetic susceptibility measurements above 3°K and Hall effect and resistivity determinations between 50 and 300°K are reported forn‐type silicon samples irradiated with increasingly higher doses of fission neutrons. The paramagnetism due to electronic states in the forbidden gap shows an initial decrease after short irradiation but a reversal, increase, and final saturation at a value less than that originally contributed to the paramagnetism by the filled donors after longer irradiation.The Hall coefficient shows evidence of a distribution of irradiation‐produced energy levels in the neighborhood of 0.3 ev below the conduction band. The mobility goes through an initial sharp decrease with irradiation but recovers partially after longer irradiations. The results are discussed in terms of several models of radiation damage. It is concluded that a simple model based on uniformly dispersed interstitials and vacancies is not adequate to explain the results and that interactions between centers, and nonuniform distribution of damage will probably have to be taken into consideration.

ISSN:0021-8979    

DOI:10.1063/1.1735291

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Electron spin resonance has been observed inn‐type silicon irradiated with 0.5‐Mev electrons. The particular resonance lines discussed here appear only in pulled crystals which contain about 1018oxygen atoms per cm3. The lines do not appear in floating zone crystals (<1017oxygen per cm3). The pattern is anisotropic with respect to the field orientation and can be fitted with agtensor with componentsg[100]=2.0029,g[110]=2.0019,g[11¯0]=2.0096.Hyperfine structure due to interactions with Si29nuclei is also observed. The hyperfine structure tensor exhibits a [111] symmetry indicating that the electron is not centered on the silicon nucleus with which it is interacting. A model is suggested, consistent with the observed symmetries, according to which vacancies produced during irradiation diffuse to the distorted regions around oxygen atoms.

ISSN:0021-8979    

DOI:10.1063/1.1735292

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The spin resonance behavior in room temperature irradiatedn‐type silicon is observed to be significantly different for silicon grown in quartz crucibles from that grown by the floating zone method. The dominant spectrum in each is discussed. The defects giving rise to the spectra are interpreted as containing impurity atoms and as having formed when the impurities trap mobile interstitials and/or vacancies. In quartz crucible grown silicon, the impurity may be oxygen. In the floating zone material, the impurity appears to be the phosphorus used in the doping. A 20°K irradiation and anneal is described which suggests the temperatures at which this defect motion is occurring. Features of the spin resonance spectra suggest that the vacancy may be the mobile effect.

ISSN:0021-8979    

DOI:10.1063/1.1735293

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The different effects of Co60gamma ray and fast neutron bombardment on the electrical behavior of germanium are discussed in terms of different local distributions of lattice defects expected for these two types of radiation. For the first of these, which is expected to introduce randomly distributed pairs of interstitials and vacancies, the state at 0.20 ev below the conduction band has been found to increase the concentration of ionized scattering centers on becoming occupied with conduction electrons. This state has been ascribed to a mobile interstitial because of its annealing behavior at moderate temperatures. Energy levels inp‐type Ge and their annealing behavior are also discussed. In neutron irradiatedn‐type germanium the behavior of Hall mobility and the apparent energy distribution of defect levels are discussed in terms of a tentative model for the potential distribution around regions of high local lattice disorder expected to result from neutron bombardment. This model postulates that the disordered region isptype and is surrounded by a positive space charge region in then‐type matrix which insulates it from the matrix. This configuration of electrostatic potential around the disordered region in effect produces an insulating region whose radius is ∼10 times that of the disordered region itself. The behavior of Hall mobility in irradiatedn‐type specimens is consistent with the predictions of this model.

ISSN:0021-8979    

DOI:10.1063/1.1735294

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The width and depth of the potential wells surrounding disordered regions in neutron irradiatedn‐type germanium and extrinsic silicon are estimated. Numerical examples of well dimensions for a wide range of sample characteristics are presented. Some effects of disordered regions, e.g., (a) scattering of conduction electrons, (b) absorption of holes, and (c) polarizability, are discussed.

ISSN:0021-8979    

DOI:10.1063/1.1735295

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The energy levels found in germanium irradiated by different particles seem at first to be mutually inconsistent. It is possible tentatively to reconcile the differences by consideration of clustering and association of defects. Four levels are ascribed to single vacancies and interstitials. A crude theory is constructed to explain these levels, particularly their asymmetrical distribution in the energy gap, and to assign each to a definite defect. This theory differs somewhat from a previous one due to James and Lark‐Horovitz; some differences in experimental predictions are discussed in particular.

ISSN:0021-8979    

DOI:10.1063/1.1735296

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Radiation‐induced energy levels in silicon have been detected, positioned, and evaluated with the help of many techniques. In this paper, the presently available body of information has been organized, summarized, and analyzed. A short historical review precedes a critical discussion of evidence recently reported for electron‐, deuteron‐, and neutron‐irradiated silicon. Three conclusions emerge from such a confrontation: (1) the energy level pattern is essentially independent of the damaging agent; (2) the pattern seems to present a remarkable symmetry with respect to the middle of the gap; (3) shallow levels close to the band edges are introduced in similar concentrations and at higher rates than the deep traps. On this basis, an attempt is made to interpret the infrared absorption and photoconductivity data of Fan and Ramdas. Problems such as those associated with the charge state of radiation‐induced defect centers are examined in the light of a novel experimental approach.

ISSN:0021-8979    

DOI:10.1063/1.1735297

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Electron‐bombardment damage in oxygen‐free silicon is compared with that found in pulled crystals which have been previously reported. It is found, in agreement with conclusions drawn from spin resonance experiments, that the level 0.16 ev below the conduction band is associated with oxygen. In oxygen‐free silicon a deep level, 0.38 ev below the conduction band is produced in dominant density, and a broad shallow level in lesser concentration. The 0.16‐ev level is not produced. The difference between this level scheme and that found in pulled crystals which contain oxygen points up the hitherto unsuspected importance of impurities in the formation of the stable defects, during the rearrangement of the vacancies and interstitials produced by the primary displacement.

ISSN:0021-8979    

DOI:10.1063/1.1735298

出版商:AIP    

年代:1959

数据来源: AIP