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Oxygen '96

Early Stages of Oxygen Precipitation in Silicon

INFLUENCE OF ISOVALENT DOPING ON THE PROCESSES OF THERMAL DONORS FORMATION IN SILICON

L. Khirunenko, V. Shakhovtsov V. Shumov and V. Yashnik

Institute of Physics of the National Academy of Sciences of Ukraine 252650, Kiev-22, Pr.Nauki 46, Ukraine

Key words: oxygen, silicon, germanium, thermal donors

It is known the efficiency of oxygen-related thermal donors (TD) formation in silicon depends on its impurity composition. Especially it is concerned isovalent impurities such as C and Ge.

In this work the investigation of influence of doping with germanium on the processes of low temperatures (450 degrees C) thermodonors formation in Si are presented. The concentration of Ge in Si was altered from 3x1018 to 2x1020 cm-3. The measurements were made using IR Fourier spectroscopy.

We have observed appearance of new additional TD absorption lines and also complex structure of individual bands at the concentration of Ge more than 5x1018 cm-3 in Si. The energy position of these lines is very close to that for lines observing in specially undoped Si. Using illumination the components connected with transitions from exited states were distinguished. Three groups of lines connected with new TD types in Si were identified using the calculations in the effective mass theory approximation.

Investigations of differential spectra have shown that as concentration of Ge increases the efficiency of formation of TD typical for specially undoped Si gradually is decreased. At the same time the efficiency of introduction new TD is much lower in Si than that in Si. As a result, beginning from concentration of Ge 1019 cm-3 increasing of thermal stability of Si is observed. At the concentration of Ge about 1020 cm-3 the total concentration of TD decreases more than an order of magnitude.

It was shown that effect of decreasing of TD formation takes place also for "shallow" thermodonors (EI=0.036 eV) which appear at the initial heat treatment stage (1-5 hours).

Observed effects are explained by formation a new type origin of TD centres in Si at doping with Ge arising as a consequence of correlated distribution of atoms Ge and Si.


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Last modified: Mon Feb 19 12:11:08 GMT 1996 JG
                                                                                                                                                                                                                                                                       

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