AVS 45th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuM

Paper TF-TuM10
Germanium Films and Their Application in Cryogenic Temperature Sensors

Tuesday, November 3, 1998, 11:20 am, Room 310

Session: Thin Films for Sensing and Data Storage
Presenter: V.F. Mitin, Microsensor Co. Ltd., Ukraine
Authors: N.S. Boltovets, State Research Institute "Orion", Ukraine
J.P. McFarland, University of Florida
G.G. Ihas, University of Florida
R.V. Konakova, Microsensor Co. Ltd., Ukraine
V.F. Mitin, Microsensor Co. Ltd., Ukraine
Correspondent: Click to Email
The principal objectives of our work were: (i) to prepare Ge films on GaAs suitable to develop temperature sensors; (ii) to study the structure and electrical properties of Ge films; (iii) to develop and design miniature wide-range thermometers capable of operating in the 30 mK to 300 K temperature range; and (iv) to investigate sensors at low temperatures and in high magnetic fields. The films have been prepared by Ge thermal evaporation in a vacuum on semi-insulating GaAs substrates. The electrical properties of the films obtained depended on the details of their fabrication. To fabricate a resistance temperature sensor capable of operating over a wide temperature range, several different conduction mechanisms are to be realized in the Ge film, each of which providing thermo-sensitivity in its own temperature range. This may be achieved through multi-component doping and compensation of the Ge film. At least three main sources of extra charge carriers exist in the Ge films on the GaAs substrates; namely, Ga and As atoms and structural defects. A relationship between them is determined by the film growth conditions. By varying the conditions during the film fabrication, one can prepare Ge films having different doping levels and degrees of compensation, i.e., different thermo-sensitivities. In this way, temperature sensors having different thermometric characteristics and capable of operating over different temperature ranges can be produced. Films with a monotonic temperature dependent resistance in the 30 mK to 300 K range have been fabricated. We present the miniature temperature sensor design based on Ge films, and results of sensor investigation in this temperature range and in magnetic field up to 6 Tesla. We also discuss the mechanism of conductivity in the films responsible for magneto- and thermo-sensitivity.