FAR INFRARED Ge DETECTORS: CONDUCTION AND ABSORPTION MECHANISMS
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This report describes an experimental study of the conduction
and absorption mechanisms of Germanium in the temperature range 4.2 -
1.5 K. The results of these studies were mainly devoted to the developments
of very far infrared detectors.
Germanium (Ge) is a well-known semiconductor element used
widely, when doped with small concentration of impurities, for detection
of far infrared wavelengths up to 100~m. For doping concentrations less
16 3 than 1.0 x 10 atoms/em, the absorption of radiation in the range 100-
1000~m is very weak Because of the lack of the proper absorption mechanisms,
except for some photo-hopping absorption in compensated samples
around 1000llm.16 -3
In the range of doping between 1-8 x 10 cm ,there
exists additional thermal activation energy not present in the lower
concentrations. It was thought that this activation energy results from
impurity interactions in this doping range, and hence a delocalized energy
band is thus formed above the ground state level. However, the electrical
conduction, the width of this band and its position, and the relevance of
this band to the marked bolometric effect for 10o-lOOOWU wavelength detections are not yet clear.
This thesis presents further study on this band together with its
relation to the conduction and absorption mechanisms. Comparative studies
were usually made for two samples of Ge differing in doping configuration,
one of which does not have this additional activation energy (low concentration)
.
The firs two chapters give a review of the absorption and conduction
mechanisms in Ge at low temperatures, and the performance relations
and measurements for different types of infrared detectors.
In this report, the conduction mechanism is studied for the two
samples, and includes galvanometric properties, thermal properties and
energy scattering processes for the carriers in the delocalized band.
The absorption characteristics, 1n lOO-lOOO~ru range of the
two samples were investigated.
Germanium elements with absorbing surfaces are also studied
using two different techniques, namely, surface ion implantation and
metal film deposition. The mutual effects of the implanted surface
and the bulk material are discussed and suggestions for the future of
this technique are given.
Finally, the design and performance of the constructed high
sensitivity far infrared Ge detectors using the higher concentration
sample are given. Theoretical noise limitations were reached in these
detectors. Heasurements and practicaI. astronomical applications are
also given.
Authors
El-Atawy, SAMIR ABDALLAHCollections
- Theses [4190]