Impact of Boron and Gallium on Defects Production in Silicon
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Impact of Boron and Gallium on Defects Production in Silicon Aurangzeb Khan1, Nethaji Dharmarasu1, Masafumi Yamaguchi1, Kenji Araki1, Tuong K.Vu1, Tatsuo Saga2, Takao Abe3, Osamu Annzawa4, M. Imaizumi4 and Sumio Matsuda4 1 Toyota Technological Institute, 2-12-1 Hisakata, Tempaku, Nagoya 468-8511,Japan 2 Sharp Corporation, 282-1 Hajikami, Shinjo, Kitakatsuragi, Nara 639-2198, Japan 3 Shin-Etsu Handotai Co., Ltd, 2-13-1 Isoba, Annaka, Gunma 379-0196, Japan 4 National Space Development Agency of Japan, 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505, Japan.
ABSTRACT We report the results of comparison of radiation-induced defects (1 MeV electrons) in n -p-p Si diodes doped with gallium or boron ranging in concentration from 8 x 1014 to 5 x 1016 cm-3, together with the impact of oxygen on radiation –induced defects. Present results provide evidence for new defects states in addition to those previously reported in galliumand boron-doped Si. The combined boron and gallium data provide enough information to gain valuable insight into the role of the dopants on radiation-induced defects in Si. The interesting new future of our results is that the gallium appears to strongly suppress the radiation induced defect, especially hole level EV+0.36 eV, which is thought to act as a recombination center. Similarly the dominant electron level at EC-0.18 eV in B-doped Si (which act as a donor) has not been observed in Ga-doped CZ-grown Si. +
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INTRODUCTION Recently [1], It has been observed that light or carrier injection induced degradation of Czochralski-grown silicon (Cz-Si) is due to the formation of boron-oxygen complex. An approach to avoid the deleterious effects of the boron-oxygen complex is to use different dopants, such as Ga, which shows no light degradation in Si Solar cells. In order to clarify the potential of Ga-doped Si solar cells for space applications in comparison with B-doped Si cells, we report the results of comparison of radiation-induced defects (1 MeV electrons) in n+-p-p+ Si diodes doped with gallium or boron ranging in concentration from 8 x 1014 to 5 x 1016 cm-3. The purpose of comparison is also to clarify the effects of different impurities on microstructural changes, which occur in Si during radiation. Present study also compare and discuss the isochronal annealing recovery of the radiation induced defects both gallium or boron doped n+-p-p+ Si solar cells solar cells and single crystal after 1 MeV electron irradiation and is correlated with changes in the Deep Level Transient Spectroscopy (DLTS) defects spectra. EXPERIMENT The fundament of the current investigation of impurity effects on radiation-induced defects in Si is a set of wafers grown by Shin-Etsu Handoti, Japan. The different types of boron and gallium doped wafers grown either with the Czochralski (CZ), magnetic R9.7.1/O14.7.1
Czochralski (MCZ) or float zone (FZ) method with doping and oxygen concentrations were used. The diodes structure was similar to the structure used in previous studies [5,6, 8]. The area of 2 x 10-6 ~ 4 x 10-6 m2 was de
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