INFRARED VIBRATIONAL BANDS RELATED TO THE THERMAL DONORS IN SILICON

Two groups of infrared (IR) localized vibrational bands in the regions 975-1015 and 724-748 cm(-1) have been correlated with the well-known IR electronic bands due to the thermal double donors (TDs) and with th e TD concentration from resistivity measurements. The two groups are s uggested to be due to two different vibrational modes of Oxygen atoms in a TD core. The vibrational bands at 975, 988, 999,and 1006 cm(-1) a re correlated to TD1, TD2, TD3, and TDs greater than or equal to TD4, respectively, while the band at 1012 cm(-1) correlates to the NL10 cen ter. A calibration coefficient for the TD-related vibrational bands wa s determined. This calibration coefficient can be used to estimate the sizes of the TD-related centers, assuming that the calibration coeffi cient for interstitial oxygen is applicable on the oxygen atoms of the se centers. This results in that all of the TD-related bands originate s from centers of 1-2 oxygen atoms, suggesting these bands to be due t o the vibrations of oxygen atoms in a TD core. The different positions of the TD-related bands could be explained by differently strained en vironments caused by different oxygen clusters. It is suggested that t hese clusters will develop into larger oxygen precipitates, which at t he end of TD formation appear in the spectrum with a broad IR band at about 1060 cm(-1). The early stages of the TD formation at temperature s below about 450 degrees C are closely related to a transformation pr ocess of preexisting clusters related to the 1012 cm(-1) band. This ex plains the formation of the early TDs at low temperatures, when the in terstitial oxygen concentration is nearly constant. (C) 1996 American Institute of Physics.