Electrical characterisation of impurities and defects in semiconductors

The electrical properties of foreign atoms in semiconductor crystals are of vital importance for the fabrication of semiconductor devices. Device performance relies on intentional doping with donor or acceptor elements but may be adversely affected by contamination with unwanted impurities.

We progressively developed the concept of variable temperature spreading-resistance profiling (VT-SRP). This extension of the conventional room temperature SRP technique allows to combine the measurement of an impurity depth profile with the determination of the main impurity-related electronic defect level. This unique feature was exploited on Ge crystals containing e.g. diffusion-induced Au profiles. Another promising application concerns the analysis of diffusion profiles for elements that occur in various defect states. This potential of VT-SRP was demonstrated on Si samples diffused with sulphur or selenium as these elements may be present both as isolated atoms and pairs. Given the well-known energy levels of both S or Se configurations in Si we were able to resolve not only the shape and depth of the diffusion profile but also the ratio of isolated atoms to pairs in the diffusion zone.

Deep level transient spectroscopy (DLTS) was used to investigate the electrical properties of the double acceptor Zn in Si_1-xGe_x alloys as a function of composition x. For the first time the systematic variations of impurity-related ionisation enthalpies were obtained over a large SiGe composition range. As a special feature it was observed that the emission of electron holes is strongly influenced by statistical variations in the number of Si and Ge atoms in the vicinity of the substitutionally dissolved Zn impurity.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft

Beteiligte Wissenschaftler:

Dr. H. Bracht, Prof. Dr. W. Gehlhoff (TU Berlin), Dr. P. Kringhoj (Chalmers University of Technology, Göteborg), Dr. K. Laßmann (Universität Stuttgart), Dr. A. Näser (TU Berlin), Dr. A. Nylandsted-Larsen (Chalmers University of Technology, Göteborg), Dr. H. Overhof, Dr. H. Schroth (Universität Stuttgart), Dr. N. A. Stolwijk, Dipl.-Phys. S. Voß

Veröffentlichungen:

Voß, S., H. Bracht, N. A. Stolwijk: High-temperature spreading-resistance profiling for the characterization of impurity distributions in n-type silicon, Mater. Sci. Semicond. Process. 4 (2001) 67 - 70

Voß, S., H. Bracht, N. A. Stolwijk: Low-temperature spreading-resistance profiling for the characterization of impurity distributions in germanium, Physica B 273 - 274 (1999) 561

Masuhr, A., H. Bracht, N. A. Stolwijk, H. Overhof, H. Mehrer: Point defects in silicon after zinc diffusion - a deep level transient spectroscopy and spreading resistance profiling study, Semiconductor Science and Technology 14 (1999) 435 - 440

Gehlhoff, W., A. Näser, H. Bracht: EPR proof of the negatively charged acceptor state Zn^-_s in silicon, Physica B 273 - 274 (1999) 264 - 267

Schroth, H., K. Laßmann, S. Voß, H. Bracht: Reduction of the spin-orbit splitting of the deep acceptor ground state of Zn^-_s in Si, Physical Review Letters 85 (2000) 417 - 420