Thesis--Brunswick. / In Periodical Room.

Berlin, Humboldt-Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Berlin, Humboldt-Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Hannover, Universiẗat, Diss., 2002.

Berlin, Humboldt-Universiẗat, Diss., 2001.

Heidelberg, Universiẗat, Diss., 2003.

Th.--Sci. phys.--Grenoble 1, 1978. N°: 154. / Extr. en partie du Journal de physique ; de Zeitschrift für Physik. A, 278, 1976, 189-199 ; de Nuclear physics. A, 308, 1978, 103-124 ; 313, 1979, 45-76 ; de Physical review. C, 13, 1976, 6 et de Nuclear data tables, 11, 1973, 351-357.

The drift velocity of electrons in n-type germanium has been measured as a function of applied electric field at lattice temperatures of 77°K and 295°K. Three directions of applied field were used, viz. (1, 0, 0), (1, 1, 0) and (1, 1, 1) crystal directions. The range of field strength was from 100 v/cm to 75 kv/cm. A longitudinal anisotropy was observed at 77°K but not at 295°K. At 77°K the drift velocity for a given field strength was greatest in the (1, 0, 0) direction and least in the (1, 1, 1) direction. All specimens showed saturation of the drift velocity at high fields. In no case did the drift velocity show a further increase with increasing electric field once it had saturated. At 77°K, all (1, 0, 0) specimens exhibited a breakdown effect, the cause of which is not known. Its characteristics could not be correlated with any properties of the specimens. The results are analysed on the basis of an extension of Stratton's theory to the case of a many-valley semiconductor. It is assumed that intervalley scattering does not affect energy relaxation, but does contribute a shift in the relative populations of the conduction band valleys. This theory is successful at low fields. It predicts an anisotropy at 77°K while predicting none at 295°K. However, it predicts too much anisotropy at low fields at 77°K. It also predicts an anisotropy at high fields at 295°K. Suggestions are made as to possible reasons for these discrepancies. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The intensity of optical absorption, near the absorption edge in germanium, is examined as a function of strain applied to the lattice at 90 °K. The results are interpreted in terms of the change of the band structure of the lattice with applied strain. The absorption edge in unstrained germanium shows a single sharp peak due to exciton formation, whereas the edge in the strained specimens shows two exciton peaks. The peak positions vary linearly with both compressional and tensional strain up to the maximum strains applied (0.1% deformation). The exciton binding energies in the strained germanium lattice, calculated within the effective mass approximation, are approximately equal and independent of the magnitude of the strain. The separation of the peaks gives for the shear deformation potentials, the values |b| = (2.7 ± 0.3)eV/unit <100> shear and |d| = (4.7 ± 0.5)eV/unit <111> shear. The positions of the peaks give the shift of the energy gap as - (10.3 ± 1) eV/unit dilatation. Lattice imperfections are found to have no effect on the interpretation of the results. The broad absorption edge observed in evaporated films of germanium is accounted for in terms of internal strains. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Lithium drifted germanium detectors have been prepared for use as high resolution gamma ray spectrometers. The fabrication procedure and the problems which can arise during preparation are discussed in detail. Using the techniques described, germanium detectors having the following characteristics were prepared. Active Volume 1.0 cm³ 0.5 cm³ 2.0 cm³ 1.7 cm³ Total Resolution at 661 keV 5.0 KeV 4.0 KeV 4.0 KeV 2.9 KeV / Science, Faculty of / Physics and Astronomy, Department of / Graduate