Zn‐Si‐P Layers Deposited by flash Evaporation

Abstract

I n t h e c a s e o f CuInSe2 a n d r e l a t e d compounds t h e c h e m i c a l c o m p o s i t i o n a n d t h e c r y s t a l s t r u c t u r e o f t e r n a r y s e m i c o n d u c t o r l a y e r s Lrown by f l a s h e v a p o r a t i o n a r e a b o u t t h e same a s t h a t o f t h e s t a r t i n g m a t e r i a l ( e . g . SCHULLUVld e t a l . 1 9 8 8 ) . A s i m i l a r r e s u l t w e have also f o u n d for t h e d e f e c t -c h a l c o p y r i t e ZnIn2Se4 <SCHU&lNN e t a l . ) b u t t h e films p r o d u c e d w e r e a l w a y s v e r y t h i n , p r o b a b l y o r i g i n a t e d by t h e sr.ia11 s t i c k i n g c o e ff i c i e n t o f t h e z i n c a t o m s , In t h i s p a p e r we r e p o r t a t f i r s t t i m e r e s u l t s on t h e d e p o s i t i o n o f ZnSiY2 by t h e method iiientioned above. T h i s c h a l c o p y r i t e -t y p e compound c o n t a i n s e l e m e n t s c h a r a c t e r i z e d a l s o by l a r g e d i f f e r e n c e s i n t h e v a p o u r p r e s s u r e s . The f i l m s w e r e grown by f l a s h e v a p o r a t i o n u n d e r h i g h vacuum cond i t i o n s o f a b o u t lom3 Pa. The s t a r t i n g m a t e r i a l ( Z n S i k 2 w i t h c h a l c op y r i t e s t r u c t u r e , a = 5.40 8 , c = 10.44 8 ) was powdered ( g r a i n size 125-160p-m) a n d t h e n g r a v i t y f e d t o a r e s i s t a n c e -h e a t e d t u n g s t e n b o a t h e l d a t a t e m p e r a t u r e o f a b o u t 1850 K. The s u b s t r a t e t e m p e r a t u r e s (Tsub) w e r e v a r i e d i n t h e range f r o m 595 t o 8 2 0 K i n s t e p s o f 25 K. Chemomechanically p o l i s h e d {I 11 )A-a n d !100:--oriented LEC G a A s w a s u s e d as s u b s t r a t e s . The l a y e r s were i n v e s t i g a t e d by r e f l e c t i o n h i g h e n e r g y e l e c t r o n d i f f r a c t i o n (MEED) a n d R u t h e r f o r d b a c k s c a t t e r i n g s p e c t r o s c o p y (RBS). S p i t a x i a l g r o w t h w a s f o u n d i n t h e s u b s t r a t e t e m p e r a t u r e range f r o m 695 t o 770 K f o r b o t h t h e s u b s t r a t e o r i e n t a t i o n s ( F i g . 1 , 2 ) . P o i n t r e f l e x e s o r i g i n a t e f r o m t h e l a y e r s a n d s t r e a k s f r o m t h e s u b s t r a t e s . A d d i t i o n a l p o i n t r e f l e x e s i n d i c a t e twins a l o n g { I l l ) d i r e c t i o n s a n d s t r e a k s i n (111) ( F i g . 2) p o i n t t o i n t e r f a c e s ( e . g . s t a c k i n g f a u l t s ) . B e s i d e s e p i t a x i a l g r o w t h a l w a y s amorphous i s o b s e r v e d . The e p i t a x i a l l a y e r s are v e r y t h i n ( a b o u t 50 81, b u t c o n t i n u o u s . For Tsub=670 K some p o l y c r y s t a l l i n e p a r t s a r e p r e s e n t i n t h e f i l m s i n a d d i t i o n t o amorphous a n d e p i t a x i a l . A t l o w e r s u b s t r a t e t e m p e r a t u r e s o n l y amorphous g r o w t h o c c u r s . Above 770 K n o l a y e r r e f l e c t i o n s c o u l a be d e t e c t e d .