A Study On The Deposition Of a-Si:H Films For High Photoconductivity

Abstract

A s t h e o p t i c a l band gap decreased, p h o t o c o n d u c t i v i t y i n c r e a s e d . The p h o t o c o n d u c t i v i t y was about 1 0 ' 5 1 0 4(Cicm) ' when t h e o p t i c a l band gap was below 1.75eV. The d a r k c o n d u c t i v i t y v a l u e s were i n t h e r a n g e o f 10"l-lO"o(Rcm) l. I n F i g . 2 , t h e r a t i o o f t h e i n f r a r e d a b s o r p t i o n c o e f f i c i e n t azogo t o a2000 and p h o t o c o n d u c t i v i t i e s a r e shown. The a b s o r p t i o n c o e f f i c i e n t a t 2090cm'' i s S i H 2 bond ing mode and 2000cm i s S i H b o n d i n g mode. A s t h e C C Z O ~ O / ~ Z O O O decreased, p h o t o c o n d u c t i v i t y i n c r e a s e d . When t h e r a t i o o f t h e d i h y d r i d e t o t h e monohydr ide was below 1 . 5 . h i g h p h o t o c o n d u c t i v i t y was o b t a i n e d . Monohydr ide i n a S i : H f i l m s becomes a more dominant bond ing mode w i t h i n c r e a s i n g p h o t o c o n d u c t i v i t y . We o b t a i n e d h i g h p h o t o c o n d u c t i v i t y a t l ower FWHM as shown i n F i g . 3 . The hydrogen c o n t e n t can be determined f rom t h e wagging mode(Fig.4) a t 640cm" because t h e wagging mode a b s o r p t i o n i s p r o p o r t i o n a l t o t h e t o t a l hydrogen c o n t e n t independent o f t h e bond ing c o n f i g u r a t i o n . The h i g h p h o t o c o n d u c t i v i t y about 10 '5-10 '4(Rcm) ' ' was o b t a i n e d when t h e hydrogen c o n t e n t was 1 8 2 4 a t . t . 3 H2/SiHq dependent data / Temperature depent data Photo A Power dependent data CI r 7 Pressure dependent data I 1E-4 ~ L