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The use of high om.~gnetic fields for the characterization of impurities in epitaxiai GaAs M. N AFSAR Microelectron. J. 13 (1), 15 (1982) The only reliable method for indentification of donor contaminants such as Si, S, Si, Sn and Ge in ultra-high purity epitaxial GaAs is the observation of the 1 s --* 2 p transition by means of far-infrared photoconductivity in high-intensity magnetic fields. Until recently, interpretation of this simple data has been unreliable. For example, it is found that the inhomogeneous Stark broadening of the 1 s --* 2 p (m = -1) transition of the hydrogen-like donor in VPE grown GaAs almost disappears as the magnetic field is increased to 100 kilogauss (20 tesla). Moreover, our new method of employing robe epitaxial GaAs (p-type) slightly doped with a single type of donor now provides the solution to the problem of resolving and identifying the varity of possible substitutional donors, one at a time.
Defect density and electrical properties of vacuum evaporated copper films for annealing studi~ of electrical resistance K. NARAYADAS, M. RADHAKRISHNAN and C. BALASUBRAMANIAN Electrocomponent Sci. Technol. 9, 171 (1982) Copper films (210-1650~) were deposited onto glass microslides by vacuum evaporation. The films were subjected to heat treatment at a constant rate and the variation of electrical resistance with temperature was measured. The defect density and activation energy were calculated for different thicknesses from the knowledge of the change in electrical resistance with temperature and time. The defect density, Fo(E)~,, varies from 17.2 to 6.05 #m 9 cm eV -t in the thickness range 210-1650~ whereas no appreciable variation in the activation energy is observed.
Thickness dependence of resistivity and temperature coefficient of resitivity (TCR) were studied in the above thickness range and the bulk resistivity and TCR were found to be 1.75/zt/. cm and 5.5 x 10 -2 K -t respectively. Assuming the scattering coefficient to be zero, the mean free path of conduction electrons was estimated. From the knowledge of the bulk resistivity and mean free path, the Fermi surface area and the effective free electron density per atom were evaluated as 21.86 x 1016cm -2 and 0.92 respectively.
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