Fig. 1. Schematic figures of the InGaAsP layers grown by NS MOVPE. T h f a b r i c a t i o n o f a d v a n c e e d i n t e g r a t e d m u l t i - quantum-well ( MQW ) waveguide devices and high- p e r f o r m a n c e l a s e r d i o d e s r e q u i r e s e x t r e m e l y uniform device characteristics. The selective metal- org ani c vap or pha se epi tax ial ( MOV PE ) gro wth of InG aAs P lay ers bet wee n a pai r of die lec tri c str ipe masks on a narrow stripe region ( e.g. 0.5 to 2 μ m wide) in the [011] direction of an InP (100) substrate ( F i g . 1 ) i s a n a t t r a c t i v e m e t h o d s t o f a b r i c a t e p h o t o n i c i n t e g r a t e d d e v i c e s . T h e m u l t i l a y e r t h i c k n e s s , c o m p o s i t i o n , a n d l a t t i c e s t r a i n c a n b e varied between different regions of the same wafer th ro ug h va ri at io n of th e di el ec tr ic ma sk wi dt h. In a d d i t i o n , a n i d e a l o p t i c a l w a v e g u i d e s t r u c t u r e surrounded by (100) and (111) crystal planes, can b e f o r m e d a u t o m a t i c a l l y w i t h o u t t h e n e c e s s i t y o f s e m i c o n d u c t o r e t c h i n g . U t i l i z i n g t h i s g r o w t h t e c h n i q u e , h o w e v e r , t h e l a t t i c e s t r a i n o f t h e selective MOVPE layers is difficult to control. High- resolution X-ray diffraction ( HRXRD ), possessing a HIGH-RESOLUTION MICROBEAM X-RAY DIFFRACTOMETRY APPLIED TO NARROW-STRIPE SELECTIVE MOVPE GROWN InGaAsP / InP LAYERS high-angle and/or high-reciprocal space resolution, u s u a l l y u s e d a s a s t r a i n c h a r a c t e r i z a t i o n t o o l f o r ep it ax ia l la ye rs gr ow n on to fu ll wa fe rs , ca nn ot be u s e d h e r e d u e t o i n s u f f i c i e n t s p a t i a l r e s o l u t i o n . HRXRD with micrometer-scale spatial resolution is needed. Recently, we developed an X-ray microbeam, p o s s e s s i n g l o w a n g u l a r d i v e r g e n c e a n d n a r r o w e n e r g y b a n d w i d t h , t h r o u g h t h e u s e o f p e r f e c t - c r y s t a l X - r a y o p t i c s i n c o n j u n c t i o n w i t h u n d u l a t o r rad iat ion X-r ays fro m the syn chr otr on lig ht sou rce [ 1 ] . T h e s e f e a t u r e s o f t h e X - r a y m i c r o b e a m a r e s u i t a b l e f o r H R X R D m e a s u r e m e n t s . W e h a v e applied this X-ray microbeam to the strain analysis o f n a r r o w - s t r i p e s e l e c t i v e ( N S ) M O V P E I n G a A s P layers, grown on 1.7- μ m-wide stripe regions of InP between a pair of SiO 2 mask stripes, varying width from 4 to 40 μ m. MOVPE growth was performed on a patterned substrate. Pairs of 100-nm-thick SiO 2 mask stripes (1 0 0) [ 0 1 - 1 ] [0 1 1] W m InP (1 0 0) selective grown layer 0.5 ∼ 2 μ m W m MOVPE SiO 2 SiO 2 SiO 2 SiO 2 Fig. 2. The experimental arrangement of the optics set up at BL24XU. w e r e p a t t e r n e d a l o n g t h e [ 0 1 1 ] d i r e c t i o n s o n a n n - type InP (100) substrate. The mask stripe width ( Wm ) was varied from 4 to 40 μ m while maintaining a n o p e n s t r i p e w i d t h o f 1 . 7 μ m . O p e n s t r i p e r e g i o n s w e r e s e p a r a t e d b y 3 0 0 μ m . I n G a A s P l a y e r s a n d I n P c a p l a y e r s w e r e g r o w n o n t h e u n m a s k e d r e g i o n s b y a t m o s p h e r i c - p r e s s u r e M O V P E . The experimental arrangement ( Fig. 2 ) was set up at th e Hy og o be am li ne BL 24 XU , us in g a hi gh - p r e c i s i o n g o n i o m e t e r s y s t e m w i t h b o t h h o r i z o n t a l and vertical rotation axes [1] . Producing an X-ray mi cr ob ea m wi th lo w an gu la r di ve rg en ce an d na rr ow en er gy ba nd wi dt h, we adopted the two-dimensional condensation of undulator radiation 15 keV X-rays, t h r o u g h s u c c e s s i v e a s y m m e t r i c d i f f r a c t i o n . T h i s method obtained a be am of ap pr ox im at el y 7. 3 μ m an d 6. 4 μ m at th e sample position in the horizontal and vertical directions, respectively. The estimated Si 511 asymmetric diffraction Slit Double-crystal monochromator Scintillation counter Sample Top view Side view angular divergence was 7.7 μ rad in the horizontal and 5.3 μ rad in the vertical directions, respectively, w i t h a n e s t i m a t e d e n e r g y b a n d w i d t h o f 6 6 m e V . W e p e r f o r m e d H R X R D m e a s u r e m e n t s u s i n g t h e microbeam in conjunction with a high-precision θ - 2 θ g o n i o m e t e r w i t h s u b m i c r o n - p r e c i s i o n X Y Z sample positioning stages. Rocking curves around the InP 400 diffraction peaks were measured using angular steps of 0.004 ° . The rocking curves from the NS MOVPE grown regions and the non-selective growth region of the sample revealed clear peak shifts in the InGaAsP layers as the mask width increased from the higher angle side to the lower angle side of the substrate p e a k s ( F i g . 3 ) . A n a l y s i s o f t h e s e r o c k i n g c u r v e s en ab le s th e pr ec is e de te rm in at io n of st ra in ( ∆ d /d ) ( F i g . 4 ) , i m p o r t a n t f o r c r e a t i n g a w e l l - c o n t r o l l e d wa ve gu id e st ru ct ur e wi th ex ce ll en t cr ys ta l qu al it y. Fig . 4. Ma sk wi dt h de pe nd en ce of th e perpendicular strain ∆ / ∆ d. Fig. 3. A series of the rocking curves from the NS MOVPE growth regions. Shigeru Kimura F u n d a m e n t a l R e s e a r c h L a b o r a t o r i e s , NEC Corporation E-mail: s-kimura @ bl.jp.nec.com References [1] Y. Tsusaka et al. , Jpn. J. Appl. Phys. 39 (2000) L635. [ 2 ] S h i g e r u K i m u r a , H i d e k a z u K i m u r a , K e n j i K o b a y a s h i , T o m o a k i O o h i r a , K o i c h I z u m i , Yusataka Sakata, Yoshiyuki Tsusaka, Kazushi Y o k o y a m a , S h i n g o T a k e d a , M a s a f u m i Urakawa, Yasushi Kagoshima and Junji Matsui, Appl. Phys. Lett. 77 (2000) 1286. -10 -5 0 5 10 15 20 25 Intensity ( arb. units) ∆ ∆ q / q ( × × 10 -3 ) 10 3 10 4 10 5 4 μ m 5 μ m 6 μ m 8 μ m 10 μ m 12 μ m 15 μ m 20 μ m 25 μ m 30 μ m 40 μ m 0 5 10 15 20 25 30 35 40 -25 -20 -15 -10 -5 0 5 Mask width ( μ μ m ) SiO 2 W m W m 1.7 μ m InP InGaAsP ∆ ∆ d / d ( × 10 -3 )
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