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THEORY OF DISPERSION AND INSTABILITIES ASSOCIATED WITH LOCALIZED POLARITONS AT
SEMICONDUCTOR INTERFACES
B. Martin, R. Wallis
To cite this version:
B. Martin, R. Wallis. THEORY OF DISPERSION AND INSTABILITIES ASSOCIATED WITH LO-
CALIZED POLARITONS AT SEMICONDUCTOR INTERFACES. Journal de Physique Colloques,
1984, 45 (C5), pp.C5-255-C5-259. �10.1051/jphyscol:1984538�. �jpa-00224156�
J O U R N A L DE PHYSIQUE
Colloque C5, supplbrnent au n04, Tome 45, avril 1984 page c5-255
THEORY OF DISPERSION AND INSTABILITIES ASSOCIATED WITH LOCALIZED POLARITONS AT SEMICONDUCTOR INTERFACES
B . G . Martin and R.F. wallis*
Aerojet GZectrosysterns, Lzusa, CA 9 1 7 0 2 , U.S.A.
*physics Dept., University o f CaZifor-nia, I r v i n e , CA 92717, U.S.A.
Resume - Nous
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o b t e n o n s l a r e l a t i o n d e d i s p e r s i o n d e s p o l a r i t o n s i n t e r f a c e s d e s e m i c o n d u c t e u r s e n u t i l i s a n t l ' a p - l e x i o n s p 6 c u l a i r e d e K l i e w e r e t F u c h s . Nous a v o n s f a i t d e s c a l c u l s s p e c i f i q u e s d a n s l a l i m i t e n o n r e t a r d e e e t a v o n s t r o u v e d e s i n s t a b i l i t e s d a n s c e r t a i n e s gammes d e f r e - q u e n c e .
A b s t r a c t - The d i s p e r s i o n r e l a t i o n f o r l o c a l i z e d p o l a r i t o n s a t s e m i c o n d u c t o r i n t e r f a c e s h a s b e e n d e r i v e d u s i n g t h e s p e c u l a r r e f l e c t i o n a p p r o a c h o f K l i e w e r and F u c h s . S p e c i f i c c a l c u - l a t i o n s h a v e b e e n made i n t h e n o n r e t a r d e d l i m i t , and i n s t a - b i l i t i e s h a v e b e e n f o u n d i n c e r t a i n f r e q u e n c y r a n g e s .
S u r f a c e and i n t e r f a c e p o l a r i t o n s h a v e b e e n t h e s u b j e c t o f n u m e r o u s i n v e s t i g a t i o n s o v e r t h e p a s t d e c a d e . T h e i r p r o p e r t i e s s u g g e s t t h e p o s s i b i l i t y o f e x p l o i t a t i o n i n i n t e g r a t e d o p t i c s d e v i c e s . F o r s u c h a p p l i c a t i o n s , i t is o f i n t e r e s t t o d e t e r m i n e t h e f e a s i b i l i t y o f a m p l i - f y i n g l o c a l i z e d p o l a r i t o n s . One p o s s i b i l i t y i s t o d e v e l o p a n a l o g u e s o f d e v i c e s F a m i l i a r i n p l a s m a p h y s i c s , s u c h a s t h e r e s i s t i v e - w a l l a m p l i f i e r /1/ w h i c h h a s b e e n u s e d t o a m p l i f y m i c r o w a v e s o r a m p l i f i e r s b a s e d on t h e w e l l known t w o - s t r e a m i n s t a b i l i t y .
I n t h e p r e s e n t p a p e r , w e e x t e n d p r e v i o u s work / 2 , 3 / t o t h e c a s e w h e r e two s e m i c o n d u c t o r m e d i a c o n t a i n i n g f r e e c h a r g e c a r r i e r s a r e i n c o n t a c t a l o n g a p l a n a r i n t e r f a c e and a r e s u b j e c t e d t o a c o n s t a n t e l e c t r i c
f i e l d p a r a l l e l t o t h e i n t e r f a c e . The d i s p e r s i o n r e l a t i o n f o r p o l a r i t o n s l o c a l i z e d a t t h e i n t e r f a c e i s d e r i v e d u s i n g t h e s p e c u l a r r e f l e c t i o n a p p r o a c h o f K l i e w e r and F u c h s / 4 / and n e g l e c t i n g c a r r i e r d a m p i n g . N a r n e r i c a l r e s u l t s a r e p r e s e n t e d f o r s e v e r a l c a s e s o f
i n t e r e s t i n t h e n o n r e t a r d e d l i m i t .
O u r s y s t e m c o n s i s t s o f a d o p e d s e m i c o n d u c t o r w i t h d i e l e c t r i c f u n c t i o n tz1(Z,u) o c c u p y i n g t h e h $ l f - s p a c e z < 0 and a s e c o n d s e m i c o n d u c t o r w i t h d i e l e c t r i c f u n c t i o n E ( k , u ) o c c u p y i n g t h e h a l f - s p a c e z > 0. A s t a t i c e l e c t r i c f i e l d i s t a k g n t o b e i n t h e y - d i r e c t i o n , a s i s t h e d i r e c t i o n o f p r o p a g a t i o n o f t h e i n t e r f a c e p o l a r i t o n . The e l e m e n t s o f t h e d i e l e c t r i c t e n s o r f o r a s e m i c o n d u c t o r c o n t a i n i n g f r e e c h a r g e c a r r i e r s
i n t h e p r e s e n c e o f a s t a t i c e l e c t r i c f i e l d c a n b e o b t a i n e d from t h e t r a n s p o r t e q u a t i o n f o r a n a v e r a g e c a r r i e r
and t h e c o n t i n u i t y e q u a t i o n
w h e r e $, m , q , v , and n a r e t h e c a r r i e r v e l o c i t y , e f f e c t i v e m a s s ,
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1984538
C5-256 J O U R N A L DE PHYSIQUE
c h a r g e , c o l l i s i o n f r e q u e n c y , and c o n c e n t r a t i o n , r e s p e c t i v e l y , $P i s t h e c a r r i e r t h e r m a l p r e s s u r e g r a d i e n t , % a n d k a r e t h e t o t a l e l e c t r i c and m a g n e t i c f i e l d s , r e s p e c t i v e l y , and a d o t o v e r a s y m b o l i n d i c a t e s a t i m e d e r i v a t i v e . E q u a t i o n s ( 1 ) and ( 2 ) c a n b e l i n e a r i z e d i n t e r m s o f t h e d e v i a t i o n s o f t h e q u a n t i t i e s f r o m t h e i r u n i f o r m and s t a t i c v a l u e s d e n o t e d b y a s u b s c r i p t z e r p . Assuming t h a t t h e d e v i a t i o n s v a r y i n s p a c e and t i m e a s e x p l i [ % o r - w t ) ] , w h e r e 2 i s t h e wave v e c t o r a n d w i s f r e q u e n c y , t h e e l e m e n t s o f t h e c o n d u c t i v i t y t e n s o r c a n b e w r i t t e n i n t h e f o r m
..
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T h e d i e l e c t r i c t e n s o r o f a s e m i c o n d u c t o r medium i s r e l a t e d t o t h e c o n d u c t i v i t y t e n s o r b y
w h e r e E~ i s t h e b a c k g r o u n d d i e l e c t r i c c o n s t a n t .
U s i n g t h e s p e c u l a r r e f l e c t i o n a p p r o a c h o f K l i e w e r and F u c h s / 4 / , o n e c a n o b t a i n t h e d i s p e r s i o n r e l a t i o n f o r i n t e r f a c e p o l a r i t o n s i n t h e p r e s e n c e o f t h e e l e c t r i c c u r r e n t s i n t h e two m e d i a . One p r o c e e d s b y c a l c u l a t i n g t h e t a n g e n t i a l c o m p o n e n t s o f t h e e l e c t r i c f i e l d i n t h e two m e d i a . The r e s u l t s a r e
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