D. Konig et al., Evidence of a high density of fixed negative charges in an insulation layer compound on silicon, THIN SOL FI, 385(1-2), 2001, pp. 126-131
Fur drift field generation. IS structures with a positive interface charge
in an insulator compound were developed in the 1980s and employed mainly on
field effect solar cells. While there has been a large number of publicati
ons about the positively biased insulator-semiconductor structure there has
been very little interest in its antipolar counterpart - the negatively bi
ased insulator-semiconductor structure so far. However. by using that struc
ture as a second drift field source for field effect solar cells their conv
ersion efficiency could be improved. The conventional rear surface passivat
ion of silicon active layers by shallow ultrahigh aluminium doping in order
to form a back surface field involves a high density of lattice and surfac
e defects which increase recombination rates. The structure introduced here
in is put onto a silicon layer and acts thus as an external negative drift
field source, thereby avoiding the drawbacks of ultrahigh doping. The layer
arrangement aluminiumfluoride-silicon dioxide on silicon seems to be a goo
d candidate for a negative drift field source. Experimental results which l
ed to a fixed interface charge of up to - 1.6 x 10(12) cm(-2) at the interf
ace aluminiumfluoride parallel to silicon dioxide are presented and an inte
rpretation of the fixed negative charge is given. (C) 2001 Elsevier Science
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