Germanium ultra-pure

Germanium was the first crystalline semiconductor in which a number of shallow acceptor and donor complexes were discovered that were unambiguously proven to contain hydrogen. This series of discoveries began in the 1970s when several laboratories conducted research and development efforts with the aim of producing ultra-pure Ge single crystal for radiation... 

II. Ultra-Pure Germanium Crystal Growth and Characterization... 

Fig. 7. Photothermal conductivity of n-type ultra-pure germanium, showing some hydrogen-oxygen donor and phosphorus transitions. In (b) the subscripts 1,2, and 3 of the D(H,0) symbol stand for transitions originating in the first, second and third shallower-lying ls-state. In (c) P stands for phosphorus.

Fig. 9. Arrhenius plots of the free hole concentration p (log p versus 1000/T) in two samples cut from a partially dislocated slice of ultra-pure germanium. The dislocation-free sample contains an acceptor with Ev + 80 meV. The shallow level net-concentration is the same in both samples.

Fig. 11. Capacitive transient spectra of defect states associated with dislocations in ultra-pure germanium (crystal 281 grown along [100] under 1 atmosphere of H2) The micrographs show the etch pits produced by dislocations on a (100) surface. DLTS peak b has an activation energy of Ev + 20 meV. The net-shallow acceptor concentration is 1010 cm-3.

In a very detailed EPR study, Pakulis and Jeffries (1981) and Pakulis (1983) investigated a large number of ultra-pure germanium crystals that were grown in vacuum or in a hydrogen or deuterium atmosphere. Several of the samples were dislocation free. The sensitivity of EPR was greatly... 

Contrary to silicon, very little work has been done in germanium regarding quantitative hydrogen diffusion or electric field drift studies. Such experiments may be complicated by the fact that ultra-pure germanium becomes intrinsic already at temperatures near 200 K. It would be worthwhile to explore the possibility of using lightly doped germanium for such studies in order to explore Fermi level dependent effects. 

Mr. Adrian Mears, of the Clarendon Laboratory, Oxford, kindly gave the author some ultra-pure germanium, from which several detectors have been constructed. These detectors appear to provide an overall signal-to-noise figure 2-10 times better than that of the 7102 photomultiplier. However, because of the small sensitive area, they are particularly useful in studies using monochromators. 

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