Evidence for the role of certain metallurgical flaws in accelerating electroluminescent diode degradation
- PDF / 923,045 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 45 Downloads / 149 Views
IT
is known that the quantum e f f i c i e n c y of s p o n t a n e ous e l e c t r o l u m i n e s c e n t (EL) d i o d e s and i n j e c t i o n l a s e r s m a y d e c r e a s e in the c o u r s e of o p e r a t i o n without any e v i d e n c e of m e c h a n i c a l d a m a g e (noncatas t r o p h i c f a i l u r e ) . P r e v i o u s aging s t u d i e s of GaAs d e v i c e s o p e r a t e d in the s t i m u l a t e d and s p o n t a n e o u s m o d e s at high c u r r e n t d e n s i t i e s (above m i d 104 a m p p e r sq cm) have l e d to the following c o n c l u s i o n s for n o n c a t a s t r o p h i c d a m a g e : 1) I n c r e a s e d s u r f a c e r e c o m b i n a t i o n i s not a s i g n i f i c a n t f a c t o r in the r e d u c e d quantum e f f i c i e n c y ; ~ 2) The c h a n g e s which o c c u r within the d e v i c e depend p r i m a r i l y on the c u r r e n t d e n s i t y of o p e r a t i o n and not on the o p t i c a l flux d e n s i t y in the junction r e g i o n . 2 T h e r e f o r e d e g r a d a t i o n d a t a o b t a i n e d with s p o n t a n e o u s d i o d e s b i a s e d at high c u r r e n t d e n s i t i e s a r e r e l e v a n t to l a s e r d i o d e s ; 3) A r e d u c t i o n o c c u r s in the i n t e r n a l quantum e f f i c i e n c y and s o m e t i m e s a l s o an i n c r e a s e d o p t i c a l a b s o r p t i o n in the junction region. This p a p e r p r e s e n t s e x p e r i m e n t a l e v i d e n c e of a d i r e c t c o r r e l a t i o n between c e r t a i n ]unction flaws and the d e g r a d a t i o n r a t e . We show that i m p e r f e c t i o n s such a s d i s l o c a t i o n s and Ga2Tes p r e c i p i t a t e s g r e a t l y inc r e a s e the d e g r a d a t i o n r a t e and, f u r t h e r m o r e , that the d e g r a d a t i o n r a t e d e p e n d s on the a c c e p t o r i m p u r i t y u s e d to f o r m the junction, with b e r y l l i u m - d o p e d d i o d e s d e g r a d i n g f a s t e r than e i t h e r m a g n e s i u m - o r z i n c - d o p e d d i o d e s . T h e s e o b s e r v a t i o n s a r e c o n s i s t e n t with the h y p o t h e s i s that d e g r a d a t i o n is due to the d i s p l a c e m e n t of i m p u r i t y a t o m s in the c o u r s e of o p e r a t i o n 3,4 and that d i s p l a c e m e n t i s e n h a n c e d by the s t r a i n f i e l d of c e r tain imperfections. 1 EXPERIMENTAL The d i o d e s w e r e p r e p a r e d by liquid p h a s e e p i t a x y . With the e x c e p t i o n of the d i o d e s with t e l l u r i u m d o n o r s , a l l d i o d e s w e r e f a b r i c a t e d by the d e p o s i t i o n of p+ l a y e r s (~2 x 1019 cm -s) f r o m m e l t s containing Ga, G a A s , and e i t h e r Be, Mg, or Zn onto n - t y p e (~2 x l0 ts c m -3) B r i d g m a n - g r o w n G a A s doped with s i l i c o n . The s u b s t r a t e o r i e n t a t i o n was (100). The t e l l u r i u m - d o p e d H. KRESSEL is Head, Semiconductor Optical Devices Research, RCA Laboratories, Princeton, N.J.N.E. BYER, forme
Data Loading...
