Luminescence Properties of New Donors in CZ-Silicon
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LUMINESCENCE PROPERTIES OF NEW DONORS IN CZ-SILICON Ph. VENDAGE, N. MAGNEA, and K. SAMINADAYAR Centre d'Etudes NuclIaires de Grenoble. DRF/SPh/PSC. 85 X - 38041 Grenoble C~dex ABSTRACT We report the observation of a new shallow donor center detected in CZ Silicon annealed at 6000 C, by EPR and luminescence experiments. The binding energy varies between 30 meV and 17 meV with the annealing time, showing the presence of several centers. The creation rate of these new defects is favoured in carbon rich material. This series of defects is probably one of the components of the New Donors. 1. INTRODUCTION Two classes of donors are known to be generated in annealed CZ Silicon : the well characterized 'Thermal Donors* (TD) are generated around 4500 C (1). and the "New Donors' (ND). not so precisely described, appear in the range 5008000C [2]. Photoluminescence (PL) spectra have been related to these two kinds of defects. The TD are described as broad bands on the low energy side of classical impurities bound exciton (BE) lines [31. and the ND are found to introduce other broad bands in the same energy range (3.4). We report here the PL observation of a new shallow donor center, called the F center. generated after annealing CZ silicon around 6000 C. The bound multiexciton (BMEC) structure associated to this center can be interpreted In the framework of the shell model [5] for a donor including a negative central cell potential. Simultaneously a very sharp EPR (Electron Paramagnetic Resonance) signal is observed at g = 1. 99931 + . 00005 in the same samples, which could be
associated with the resonance of an electron bound on the F-center. The F center is only observed in carbon rich material ([Csi] ; 5X10 1 6 cm- 3 ). When the annealing time increases, the bound exciton lines related to the F center shift toward higher energy. showing a decrease of the ionization energy. This behaviour, which is characteristic of the thermal donors created at 6000 C, indicates clearly that the F series is one of the components of the New Donors. 2. EXPERIMENTAL CZ SI samples have been annealed between 5000 C and 6500 C from 24 h to 360 h in an evacuated quartz tube. 01 and CSi concentrations have been deduced from room temperature IR absorption measurements. The resistivity has been measured by the four points probe method and the additional donor concentration has been deduced using the standard Irvin's curves. PL measurements were made at 2 K. The luminescence was excited by an Ar+ or a Kr+ laser, and detected after dispersion by a I m grating monochromator by a S1 photomultiplier or a Ge detector,
both cooled with liquid nitrogen.
The
EPR measurements were performed on an X-band spectrometer with a variable temperature cryostat adapted to the microwave cavity. This cavity has a window to allow illumination of the sample using a filtered 250 W xenon lamp. Typical sample has a volume of 2 x 5 x 0. 5 mm 3 . 3.
RESULTS
Mat. Res. Soc. Symp. Proc. Vol. 59. 11986 Materials Research Society
188
3. 1 Luminescence spectroscopy
I he phot
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