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X RAYS AND ELECTRON MICROPROBE ANALYSIS OF III-V SEMICONDUCTORS
C. Schiller, M. Duseaux
To cite this version:
C. Schiller, M. Duseaux. X RAYS AND ELECTRON MICROPROBE ANALYSIS OF III- V SEMICONDUCTORS. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-891-C2-894.
�10.1051/jphyscol:19842204�. �jpa-00223881�
JOURNAL DE P H Y S I Q U E
C o l l o q u e C 2 , s u p p l g m e n t au n02, T o m e 45,
f6vrier
1984page
C2-891X
RAYS AND ELECTRON MICROPROBE ANALYSIS OF 111-V SEMICONDUCTORS
C . S c h i l l e r and M. Duseaux
Laboratoires d'EZectronique et de Physique AppZique'e, 3 avenue Descartes, 94450 LirneiZ-Br&vannes, France
Rdsumd
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Le d o p a g e i s o 6 l e c t r o n i q u e d e 1 ' a r s g n i u r e d e g a l l i u m p a r 1 'indium a Gtd e ' t u d i 6 p a r t o p o g r a p h i e en t r a n s m i s s i o n d e s r a y o n s X , s p e c t r o m 6 t r i e d e s r a y o n s X e t m i c r o a n a l y s e i l a s o n d e e l e c t r o n i q u e . S u r d e s p l a q u e s toupees p a r a l l e l e m e n t 1 'axe d e t i r a g e d e InxGal-xAs, u n e c o r r e ' l a t i o n a e ' t 6 e t a - b l i e e n t r e l a c o n c e n t r a t i o n d ' i n d i u m e t l a r e p a r t i t i o n d e s d i s l o c a t i o n s . C e t t e c o r r e ' l a t i o n e s t e s s e n t i e l l e p o u r l e t i r a g e d e s c r i s t a u x p u i s q u ' e l l e perniet d e d e ' t e r m i n e r l a c o n c e n t r a t i o n o p t i m a l e d 'indium d a n s l a s o u r c e a v a n t l a c r o i s s a n c e LEC.A b s t r a c t - I s o e l e c t r o n i c d o p i n g by i n d i u m i n g a l l i u m a r s e n i d e was s t u d i e d by X r a y t r a n s m i s s i o n t o p o g r a p h y k r a y s p e c t r o m e t r y and e l e c t r o n m i c r o p r o b e a n a l y s i s . A c o r r e l a t i o n was s o o b t a i n e d b e t w e e n t h e i n d i u m c o n t e n t x o f p s e u d o b i n a r i e s In,Cal-xAs and t h e d i s l o c a t i o n d i s t r i b u t i o n on s l i c e s c u t p a r a l l e l t o t h e g r o w t h a x i s . The k n o w l e d g e o f s u c h d i s t r i b u t i o n is e s s e n t i a l f o r c r y s t a l g r o w e r s t o d e t e r m i n e t h e i n d i u m c o n t e n t i n t h e m e l t b e f o r e LLC g r o w t h .
E x t e n d e a l a t t i c e d e f e c t s s u c h a s d i s l o c a t i o n s , s t a c k i n g f a u l t s and p r e c i p i t a t e s a r e known t o h a v e d e t r i m e n t a l e f f e c t s on e l e c t r o n i c p r o p e r t i e s o f s e m i c o n d u c t o r s /1,2,3/ : c r y s t a l g r o w e r s a r e s o c o n c e r n e d w i t h d i f f e r e n t t e c h n i q u e s i n b o t h f i e l d s o f d e f e c t s a n a l y s i s s u c h a s X r a y d i f f r a c t i o n t o p o g r a p h y o r c a t h o d o l u m i n e s c e n c e mode i n s c a n n i n g e l e c t r o n m i c r o s c o p y and o f c o m p o s i t i o n a n a l y s i s o f m a j o r c o n s t i t u a n t s and i m p u r i t i e s .
The e l i m i n a t i o n o f e x t e n d e d d e f e c t s i n 111-V ccompounds h a s been s u c c e s s f u l l y a c h i e v e d f o r h i g h l y doped m a t e r i a l s w i t h s i l i c o n , s e l e n r u m o r t e l l u r i u m /4/ b u t o f t e n g e n e r a t e s p r e c i p i t a t i o n o f d o p a n t s . A new way a p p e a r s now w i t h i s o e l e c t r o n i c d o p i n y / 5 / by indium i n g a l l i u m a r s e n i d e i n t h e c a s e o f m a t e r i a l s grown by l i q u i d e n c a p s u l a t e d C z o c h r a l s k i t e c h n i q u e (LEC).
We s h a l l p r e s e n t h e r e a p p l i c a t i o n s o f d i f f e r e n t X r a y t e c h n i q u e s i n c o n n e c t i o n w i t h e l e c t r o n m i c r o p r o b e a n a l y s i s . I n t h e f i r s t c a s e , t h e s e X r a y t e c h n i q u e s a r e non d e s t r u c t i v e and a l l o w t o draw a map o f c r y s t a l l i n e d e f e c t s a s r e v e a l e d by X Ray T r a n s m i s s i o n Topography a n d t h e d i s t r i b u t i o n o f d o p a n t s o r i m p u r i t i e s by X r a y s p e c t r o m e t r y . I n t h e s e c o n d c a s e , e l e c t r o n m i c r o p r o b e a n a l y s i s was e a r l i e r p e r f o r m e d by e n e r g y d i s p e r s i v e a n a l y s i s and w i t h a b e t t e r s e n s i t i v i t y by w a v e l e n g t h d i s p e r s i v e a n a l y s i s .
The main p r o b l e m was i n f a c t t.o d e f i n e t h e optimum indium c o n c e n t r a t i o n i n g a l l i u m a r s e n i d e , a n d i n p a r t i c u l a r t o d e t e r m i n e t h e l i m i t i n g v a l u e s o f x, t h e l o w e s t t o g e t d e f e c t f r e e m a t e r i a l s and t h e h i g h e s t t o a v o i d p o l y c r y s t a l l i n e r e g i o n s .
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842204
JOURNAL DE PHYSIQUE
I
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ANALYTICAL TECHNIQUES1.1 - X r a y t e c h n i q u e s
1 . l . a
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X r a y t r a n s m i s s i o n t o p o g r a p h yX r a y t o p o g r a p h y was u s e d r a t h e r t h a n c h e m i c a l e t c h i n g a s f a r a s s a m p l e s must b e u s e d f o r d i f f e r e n t a n a l y s e s . T h i s t e c h n i q u e a l s o a l l o w s t o h a v e e a s i l y t h e e n t i r e map o f c r y s t a l l i n e d e f e c t s on as-grown i n g o t s .
These s a m p l e s were grown w i t h d i f f e r e n t e x p e r i m e n t a l c o n d i t i o n s , I n c o n t e n t i n t h e m e l t , t h e r m a l g r a d i e n t s , p u l l i n g r a t e . I n e a c h i n g o t , s l i c e s p a r a l l e l t o t h e g r o w t h a x i s (UU1) a n d w i t h a ( 1 1 0 ) s u r f a c e p l a n e were c u t , t h i n n e d and m e c h a n o c h e m i c a l l y p o l i s h e d down t o 0 . 2 t o 0.25 mm.
X ftay t o p o g r a p h s w e r e o b t a i n e d u s i n g Molybdenum Ko( 1 r a d i a t i o n : f o r ( 0 2 2 ) r e f l e c t i o n s , t h e v a l u e o f
p t (p
l i n e a r a b s o r p t i o n c o e f f i c i e n t and t t h i c k n e s s ) l i e s b e t w e e n 7 t o 10 : i n t h i s c a s e , anomalous c o n t r a s t on d e f e c t s is m a i n l y o b s e r v e d and s p a t i a l r e s o l u t i o n c o u l d be o f t h e o r d e r o f 2 t o 4pm
t o be compared t o dislocation ima e w i d t h o f 40 t o 50pm.
The d i s l o c a t i o n d e n s i t y l i m i t w i l l be i n t h e r a n g e o f l o q t o 5 1 0 ~ c m - ~ .1 . l . b
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X r a y s p e c t r o m e t r yI n K a n d L l i n e s w e r e a n a l y s e d u s i n g &hodium c o n t i n u o u s b a c k g r o u n d e x c i t a t i o n . The p o o r peak t o b a c k g r o u n d r a t i o s i n b o t h c a s e s were n e v e r t h e l e s s u s e d a s q u a l i t a t i v e a s s e s s m e n t . A s an e x a m p l e , t h e P/B o f 1 was o b s e r v e d f o r a s u b s t i t u t i o n r a t e x o f 2 . 1 0 - l . Due t o t h e p r o x i m i t y o f t h e RhKD l i n e , t h e I n K N l i n e c a n n o t be u s e f u l f o r x v a l u e l o w e r t h a n 0 . 4 7W2.
T h l s l e a d s u s t o u s e a chromium t u b e a s s o u r c e w i t h I n l i n e s and d i a p h r a g m s t o i n v e s t i g a t e t h e I n d i s t r i h u t l o n on e a c h s l i c e : i n t h i s c a s e , f o r x v a l u e o f 2.1L-L, P/B r a t i o was n e a r l y 7 and d e t e c t i o n limit l o w e r e d t o 0 . 1 l o - = .
T h i s method was s o u s e d t o s e l e c t s l i c e s s t u d i e d by o t h e r p h y s i c a l t e c h n i q u e s ( p h o t o l u m i n e s c e n c e o r a b s o r p t i o n ) a n d f o r e l e c t r o n m i c r o p r o b e a n a l y s i s .
1.2
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E l e c t r o n m i c r o p r o b e a n a l y s i sX r a y e n e r g y d i s p e r s i v e a n a l y s i s was p e r f o r m e d on a P h i l i p s SEM 501 B w i t h a S i ( L i ) d i o d e c o u p l e d t o a N o r t h e r n T r a c o r NS 880 a n a l y s e r . ZAF c o r r e c t i o n s w e r e a p p l i e d i n t h e r e v e r s e mode w i t h c a l i b r a t i o n c u r v e s ; b u t , a s f o r X r a y s p e c t r o m e t r y , t h e s e n s i t i v i t y i n t h e r a n g e o f 3 KeV f o r X r a y p h o t o n s was low and q u a n t i t a t i v e work was n o t p o s s i b l e f o r x
<
b.6W a v e l e n g t h d i s p e r s i v e a n a l y s i s was s o p e r f o r m e d i n P h i l i p s F o r s c h u n g L a h o r a t o r i u m (hamburg) by Dr P. W i l l i c h , u s i n g a n a u t o m a t i c Cameca m i c r o p r o b e ; w i t h a n a c c e l e r a t i n g v o l t a g e o f 20 K V and lnAs and GaAs a s s t a n d a r d s , u s i n g InLN 1 , G a K q a n d Ask* l i n e s , c o r r e c t e d w e i g h t f r a c t i o n s a n d a t o m i c c o n c e n t r a t i o n s i n % c a n be q u i c k l y p l o t t e d a s a f u n c t i o n o f p o s i t i o n by s t e p a n a l y s i s . A s a c o m p a r i s o n w i t h d o p i n g l e v e l s c u r r e n t l y g i v e n i.n e l e c t r o n i c t r a n s p o r t p r o p e r t i e s , f o r e x a m p l e , a v a l u e o f 10-3 f o r x c o r r e s p o n d s t o 2.2 l 0 I 9 c ~ n - ~ .
I1
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RESULTS AND DISCUSSIONThe s e l e c t i o n o f s l i c e s was d o n e by X r a y s p e c t r o m e t r y w i t h v a l u e s o f I n c o n t e n t s i n t h e r a n g e o f 0.2 t o 0.8 The f i g u r e s 1 a n d 2 s u m m a r i z e o u r o b s e r v a t i o n s and we s h a l l g i v e h e r e two e x a m p l e s f o r t h e d e f i n i t i o n o f I n c o n c e n t r a t i o n l i m i t w i t h on t h e l e f t f o r f i g u r e 1 , an I n c o n t e n t l o w e r by a f a c t o r 4 t h a n f o r f i g u r e 2. I n e a c h c a s e , t h e g r o w t h a x i s g o e s from t h e r i g h t t o t h e l e f t w i t h t h e b o t t o m a n d p o l y c r y s t a l l i n e r e g i o n on t h e l e f t .
FIGURES 1 AND 2 : Comparison o f d e f e c t d i s t r i b u t i o n and I n c o n c e n t r a t i o n a l o n g t h e g r o w t h a x i s .
S u b s c r i p t s a ) X Ray t o p o g r a p h s ;
S u b s c r i p t s b ) I n c o n t e n t a s d e t e r m i n e d by e l e c t r o n m i c r o p r o b e a n a l y s i s
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P.R. p o l y c r y s t a l l i n e r e g i o n , D.F. d e f e c t f r e e .A s w e c a n s e e on t h e X r a y t o p o g r a p h o f f i g u r e l a , t h e m a j o r p a r t o f t h e i n g o t on t h e r i g h t i s n o t d i s l o c a t i o n f r e e and a 5 mm l e n g t h a t t h e b o t t o m is d e f e c t f r e e
(DF) j u s t b e f o r e t h e p o l y c r y s t a l l i n e r e g i o n ( P R ) a t t h e t a i l o f t h e c r y s t a l . On t h e o t h e r h a n d , t h e X r a y t o p o g r a p h y o f f i g u r e 2a a p p e a r s a t more t h a n 90 X o f t h e s u r f a c e d i s l o c a t i o n a n d d e f e c t f r e e : o n l y a s m a l l zone o f 1 t o 2 mm a t t h e p e r i p h e r y o f t h e c r y s t a l is d i s l o c a t e d , b u t w i t h a s m a l l d i s l o c a t i o n d e n s i t y a s f a r a s i s o l a t e d d i s l o c a t i o n s a r e e a s i l y r e s o l v e d i n t h e s e b a n d s ( u s i n g a l a r g e r m a g n i f i c a t i o n ) . One t h i n g may be n o t e d b e f o r e t h e p o l y c r y s t a l l i n e r e g i o n a t t h e b o t t o m o f t h e l e f t : we d e t e c t a c o n t r a s t i n b a n d s which c o u l d be r e l a t e d t o d o p a n t s t r i a t i o n s e v e n w i t h a ( 0 2 2 ) d i f f r a c t i o n v e c t o r p a r a l l e l t o t h e s e b a n d s .
C2-894 JOURNAL DE PHYSIQUE
A l l t h e s e f e a t u r e s were I n f a c t e n c l e a r e d by e l e c t r o n m i c r o p r o b e measurements. The I n c o n t e n t w i l l be g i v e n u p r i g h t t h e t o p o g r a p h s w i t h v e r t i c a l a r r o w s on t h e l e f t a t t h e l i m i t o f m o n o c r y s t a l l i n e r e g i o n . We s h a l l n o t e t h a t i n t h e f i r s t c a s e where t h e t a i l i s t h i n n e r , t h e i n d i u m c o n t e n t i s s t i l l i n c r e a s i n g : on t h e c o n t r a r y f o r f i g u r e 2b, t h e r e is a d r o p i n t h e X v a l u e which r e m a i n s c o n s t a n t i n t h e p o l y c r y s t a l l l n e w h i l e d i a m e t e r r e m a i n s c o n s t a n t t i l l t h e end o f t h e g r o w t h . I n t h e m o n o c r y s t a l l i n e r e g i o n , t h e d e f e c t f r e e (DF) shows a d e c r e a s e o f I n from 0 . 7 5 t o 0 . 2 4 % and t h i s d e c r e a s e r e m a i n s up t o 2 0 mm where a x v a l u e o f 0.1
X
h a s b e e n measured ( d e t e c t i o n l i m i t i n t h e s e c o n d i t i o n s o f 0.02 L ) . L a t e r a l s c a n s i n 0 do n o t show s i g n i f i c a n t variation a l o n g a d i a m e t e r .F o r t h e f i g u r e 2b, t h e v a r i a t i o n o f I n c o n t e n t h a s t h e same s h a p e b u t t h e s l o p e is l e s s marked s t a r t i n g from 0 . 8
X
a t t h e b o t t o m and 0.2 7; n e a r t h e t o p o f t h e c r y s t a l . F o r t h e l e f t p a r t o f s c a n n i n g , s t e p s o f 0 . 5 mm were s h o r t e n e d t o 0 . 1 2 5 mm and t h e d o p a n t s t r i a t i o n s o b s e r v e d on t h e X r a y t o p o g r a p h s a r e i n t e r p r e t e d h e r e a s v a r i a t i o n s o f I n c o n t e n t a s f a r a s from p o i n t t o p o i n t , i n t h i s r a n g e o f c o n c e n t r a t i o n , d i f f e r e n c e s o f 1 0 t o 20 L a r e s i g n i f i c a n t .I t a p p e a r s h e r e t h a t t h e minimum v a l u e o f x f o r d e f e c t f r e e m a t e r i a l s marked h e r e by h o r i z o n t a l a r r o w s is 0 . 2
L.
The main a d v a n t a g e r e m a i n s a l s o t h a t s u c h i s o l e l e c t o n i c d o p i n g d o e s n o t g i v e r i s e t o p r e c i p i t a t e s a s c o n f i r m e d by TEM /7/.ACKNOWLEDGMENTS
We w i s h t o t h a n k P.J. KOKSNOER f o r t h e g r o w t h o f c r y s t a l s , W.J. BARTELS f o r h e l p f u l d i s c u s s i o n s on X Ray t o p o g r a p h y and G.M. MARTIN f o r comments on t h e m a n u s c r i p t . REFERENCES
( 1 ) PETROFF P.M., HARTkANN R . L . , Appl. Phys. L e t t e r s ,
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( 8 ) ( 1 9 7 3 ) 469( 2 ) KRESSEL H . , BUTLER J.K., S e m i c o n d u c t o r l a y e r s and h e t e r o j u n c t i o n s LEDS, Academic P r e s s New-York, ( 1 9 7 7 ) 533.
( 3 ) NAMISHI Y , , ISHIDA S . , MIYAZAMA S . , J a p . J . o f Appl. P h y s i c s , 22 ( 1 ) (1983) 54. - ( 4 ) JACOB G . , FARGES J . P . , SCHEMALI C., DUSEAUX M . , HALLAIS J., BARTELS W.J.,
HUKSNOER P . J . , J . o f C r y s t a l Growth,
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( 1 9 8 2 ) 245.( 5 ) JACOB G . , P r o c e e d i n g s o f t h e S e m i - I n s u l a t i n g 111-V M a t e r i a l s C o n f e r e n c e , E v i a n ( 1 9 8 2 ) 2.
( 6 ) G. JACOB, M. DUSEAUX, J . P . FARGES, M.M.B. V A N DEN BOOM, P . J . ROKSNOER, J . C r y s t . Growth,
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( 1 9 8 3 1 , 417( 7 ) OUSEAUX M . , SCHILLER C., CORNIER J . P . , CHEVALIER J . P . , HALLAIS J . , C o l l o q u e : P r o p r i 6 t . 6 ~ e t S t r u c t u r e d e s d i s l o c a t i o n s d a n s l e s s e m i c o n d u c t e u r s , A u s s o i s (Mars 1 9 8 3 ) , t o be p u b l i s h e d i n J o u r n a l d e P h y s i q u e .
