GaAs/In 0.1 Ga 0.9 As/GaAs º; c" e8 ý Photoreflectance ¤V R Ë ì Å

(1)

GaAs/In 0.1 Ga 0.9 As/GaAs º; c" e8 ý Photoreflectance ¤V R Ë ì Å

¤< - > · g Y @ ¹ · 9 - > Ú ^∗

% ò

z @ / < Æ § Ó ü t o < Æõ , â í ß 712-749

) ç 9

@

/½ ¨@ / < Æ § Ó ü t o < Æõ , â í ß 712-714 (2006¸ 2 Z 4 13{ 9 ~ Ã Î6 £ §)

MOCVD (metal organic chemical vapor deposition) Ð $ í © ) a GaAs/In

0.1

Ga

0.9

As/GaAs s 7 á x] X

½

+ Ë ½ ¨ ¸\ " f InGaAs 8 £ x _ ¿ ºa \ É r F g : £ ¤$ í ` ¦ photoreflectance (PR) ~ ½ ÓZ O Ü ¼ Ð ¸ % i . Õ ªo

¦ © : r PR Û ¼& 7 à Ô! 3 \ " f GaAs_ ½ × ¼Ì s\ ' aº ) a ñ 1.42 eV\ " f ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, Õ ªo ¦ In

0.1

Ga

0.9

As \ ' a > ) a ñ H ¿ ºa 70, 150 x 9 300 nm\ @ /K " f y y 1.311, 1.296 x 9 1.287 eV\

"

f ' a8 £ ¤ ÷ &% 3 . © : r x 9 $ : r \ " f Franz-Keldysh oscillations (FKOs)s In

0.1

Ga

0.9

As ü < GaAs ½ × ¼ Ì

s \ -t s \ " f ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, FKO_ Å Òl \ ¦ : x K In

0.1

Ga

0.9

As/GaAs _ > l © ° ú כ` ¦ ½ ¨

% i .

PACS numbers: 78

Keywords: F g ì ø Í , FKO, InGaAs, > l ©

I. " e Â ] Ø

þ

j H \ In ^x Ga 1−x As/GaAs s 7 á x] X ½ + Ë ½ ¨ ¸\ æ ¼s H l ó

ø Í F « Ñ Ð H GaAs l ó ø Í\ q K " f ¦ s 1 l x ¸\ ¦ t ¦, Ô

¦í HÓ ü t 0 l x ¸ 50 % & ñ ¸ 8 H InP l ó ø Í` ¦ 6 x ô Ç [1-3]. t ë ß InP H GaAs \ q K Ô ¦{ 9 u 8 ß ¼ l

M :ë H \ In x Ga _1−x As \ p u H + þ A´ òõ 8 ß ¼> { 9

#

Qè ß . " f î ß & ñ & h è \ ¦ ë ß [ þ t M : H GaAs l ó ø Í

`

¦ 6 x ô Ç . Ð: x In x Ga _1−x As/GaAs s 7 á x] X ½ + Ë ½ ¨ ¸ H F

g è Y Us $ s ¸× ¼ 1 p x \ ´ ú §s 6 x ) a [4-6].

In _x Ga _1−x As \ x 8 £ x É r Ð: x In _ ¸$ í q \ ½ × ¼Ì s

\

-t Ø Ô . s Qô Ç F g è \ 6 x ÷ & H F « Ñ\ F g :

£ ¤$ í ì r$ 3 s 6 x s ô Ç ~ ½ ÓZ O É r ¸ ì rF gZ O × æ \ photoreflectance (PR) Å Ò Ð 6 x ) a . s PRZ O É r # l

F g Ü ¼ Ð §À Ó+ þ AI _ é ß Ò oF g 7 £ ¤, Y Us $ \ ¦ Å Ò Ð s 6 x

#

r « Ñ ? /Â Ò\ -& ñ / B N © (electron-hole pair ; EHP)

`

¦ Ò q t$ í r v ¦, Å Òl & h Ü ¼ Ð ³ ð l © ` ¦ or ( Ü ¼

Ð+ f À Ó+ þ AI Ð r « Ñ\ { 9 ) a y n C_ ì ø Í Ö ¦ s \ ¦ 8 £ ¤

&

ñ H כ s 9, ì ø Í ¸^ _ ³ ð , s 7 á x] X ½ + Ë ½ ¨ ¸_ > ¢ ¸

H \ -t { ½ ¨ ¸\ ¦ ¸ H X < Å Ò Ä »6 x ô Ç ~ ½ ÓZ O s [7-9]. : r 7 Hë H \ " f H F K5 Å q Ä »l l © 7 £ x Ã Ì (metal organic

∗

E-mail: [email protected]

chemical vapor deposition; MOCVD)Z O Ü ¼ Ð SI-GaAs l ó

ø Í0 A\ In ^0.1 Ga 0.9 As8 £ x (70, 150 x 9 300 nm)` ¦ $ í © r

6 £ §, cap8 £ x Ü ¼ Ð Ô ¦í HÓ ü t` ¦ ' t · ú § H GaAs8 £ x` ¦ 150 nm` ¦ $ í © r & GaAs/In 0.1 Ga _0.9 As/GaAs ½ ¨ ¸_ F g : £ ¤

$ í

` ¦ PR ~ ½ ÓZ O Ü ¼ Ð ¸ % i .

II. ÷ m Ç ] M ö

: r ½ ¨\ 6 x ) a r « Ñ H ì ø Í] X $ í GaAs l ó ø Í 0 A\

!

Q( 8 £ x Ü ¼ Ð Ô ¦í HÓ ü t s ' t · ú § É r GaAs (i-GaAs)\ ¦ 300 nm` ¦ $ í © r Ê ê, In ^0.1 Ga 0.9 As \ x 8 £ x _ ¿ ºa \ ¦ 70, 150, 300 nm Ð y y $ í © r ( . Õ ªo ¦ cap8 £ x Ü ¼

Ð Ô ¦í HÓ ü t s ' ÷ &t · ú § H GaAs\ ¦ 150 nm $ í © r GaAs/In _0.1 Ga _0.9 As/GaAs ½ ¨ ¸\ ¦ ° ú H 3 > h_ r « Ñ\ ¦ 6

x % i . s z ´+ « >_ 8 £ ¤& ñ ¸| É r pump beam Ü ¼ Ð He- Ne (632.8 nm) Y Us $ \ ¦ 6 x % i ¦, Å Ò Ã º H F g é ß 5 Å q l

\ ¦ 6 x # ¸r ( . Õ ªo ¦ F g " é ¶ Ü ¼ Ð H 250 W _

) í Û ¼J $ ½ + É Ð p Ï þ á Ô\ ¦ 6 x % i Ü ¼ 9, í& h o 0.75 m é ß Ò o o © u \ ¦ : x # : r probe F g` ¦ r « Ñ\ { 9 r

& s M : ì ø Í ) a F g` ¦ z ´o B H F g Ø ¦ l Ð Ø ¦ % i .

F

g Ø ¦ l \ " f Ø ¦ ) a ñ H 7 £ x; ¤ l (pre-amplifier)\ ¦ :

x K 7 £ x; ¤ Ê ê, lock-in amplifier Ð ½ © o ) a ¸ ì ø Í Ö ¦

-420-

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Fig. 1. Photoreflectance spectra of three GaAs/In _0.1 Ga

0.9 As/GaAs heterostructures for various thicknesses of the In _0.1 Ga _0.9 As epilayer.

(∆R/R)` ¦ ½ ¨ô Ç Ê ê PC Ð : x K Û ¼& 7 à Ô! 3 Ü ¼ Ð ? /% 3

.

III. + s ÇÊ Ý õ m Í À X Ø8 ý

Fig. 1 É r 300 K \ " f 8 £ ¤& ñ ô Ç GaAs/In _0.1 Ga _0.9 As/GaAs

½

¨ ¸_ PR Û ¼& 7 à Ô s . s Õ ªa Ë >\ " f 1.42 x 9 1.30 eV

\

" f ' a8 £ ¤ ) a ñ H y y GaAs x 9 In 0.1 Ga 0.9 As _ { ç ß

\ -t s . Õ ªo ¦ In ^0.1 Ga 0.9 As ü < GaAs_ > s

\ { 9 & ñ ô Ç Å Òl \ ¦ t H 1 l x[ þ t (OS region) s ¸ H r

« Ñ\ " f ' a8 £ ¤ ÷ &% 3 H X <, s H Franz-Keldysh oscillations (FKOs) ´ òõ s .

¦ l © % ò % i _ PR ñ\ " f ' a8 £ ¤ ÷ & H FKO ÐÂ Ò'

½ × ¼Ì s \ -t H 6 £ §d Ü ¼ Ð ³ ð & ³ ) a [10-12].

E _j = ~ΩF j + E _g (1) F _j = [ 3π

2 (j − 1

2 )]

²³

, j = 1, 2, 3, 4, 5 · · ·

#

l " f E j H FKO _ j P : x ß ¼ \ -t s ¦, E g H ½

×

¼Ì s \ -t s . Õ ªo ¦ Ã º ~Ω É r 6 £ §d Ü ¼ Ð ³ ð & ³ ) a

.

~Ω = ( e ² ~ ² E ²

2µ )

¹³

(2)

Fig. 2. The linear fittings of the extreme energies in the PR spectra from the asymptotic Franz-Keldysh model.

d

(2)\ " f e H _ , µ H ü < Á º î r & ñ / B N

\

@ /ô Ç ¨ 8 í ß | 9 | ¾ Ó, Õ ªo ¦ E H l © s . F j \ É r E j _ Õ ªA á Ô\ " f f õ E j » ¡ ¤ õ _ §& h É r E g s ¦, Õ ªa Ë >

_

l Ö ¦ l ÐÂ Ò' d (2)\ ¦ 6 x # l © ` ¦ ½ ¨½ + ÉÃ º e

. InGaAs ¿ ºa 70, 150 x 9 300 nm\ @ /ô Ç ½ × ¼Ì s \

-t \ ¦ ½ ¨ô Ç õ y y 1.311, 1.296, 1.287 eV % i Ü ¼ 9, InGaAs ¿ ºa 7 £ x ½ + É Ã º2 ¤ ½ × ¼Ì s \ -t y è % i

. s H ¿ ºa ¿ º Ö ¦ Ã º2 ¤ strain % ò ¾ Ós & t l M :ë H s

. Õ ª Q [ j r « Ñ ¸¿ º PR Û ¼& 7 à Ô \ " f InGaAs

ñ ¸ ú ' a8 £ ¤ ÷ &% 3 l M :ë H \ , InGaAs \ x 8 £ x É r e > ¿ ºa

A \ $ í © ÷ &% 3 ¦ ½ + É Ã º e . Fig. 2 H y r « Ñ\ @ / ô

Ç F j \ @ /ô Ç E j ü <_ ' a > \ ¦ ? /% 3 . s Õ ªa Ë >_ l Ö

¦ l ÐÂ Ò' 300 K\ " f l © É r InGaAs r « Ñ_ ¿ ºa

70, 150 x 9 300 nm\ @ /K " f y y 2.66 × 10 ⁵ , 2.72 × 10 ⁵ Õ

ªo ¦ 2.78 × 10 ⁵ V/cm s % 3 .

Fig. 3(a),(b) x 9 (c) H y r « Ñ_ : r ¸ _ > r$ í \ @ /ô Ç PR Û ¼& 7 à Ô s . Õ ªa Ë >\ " f : r ü < ° ú s PR ñ_ + þ A I

H ¸ H r « Ñ\ @ /K _ Ä » ô Ç â ¾ Ó` ¦ Ð% i Ü ¼ 9, InGaAs x 9 GaAs\ ' aº ) a ñ H : r ¸ 7 £ x ½ + É Ã º2 ¤

¦ \ -t Ð s 1 l x ÷ &% 3 . s H & ñ Ø ½ Ó H d Ü ¼ Ð

K ? /Â Ò " é ¶ ç ß _ o Y O # Qt l M :ë H s .

Fig. 3 Ü ¼ ÐÂ Ò' : r ¸ _ > r$ í \ É r > l © ° ú כ

`

¦ ½ ¨ô Ç õ \ ¦ Table 1 \ ? /% 3 . Table 1\ Ð H

ü < ° ú s [ j r « Ñ ¸¿ º : r ¸ 7 £ x ½ + É Ã º2 ¤, l © ° ú כ

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Fig. 3. PR spectra of GaAs/In 0.1 Ga 0.9 As/GaAs heterostructures with various measurement temperatures.

Table 1. Electric fields in GaAs/In0.1Ga0.9As/GaAs heterostructures.

Sample (nm) 70 150 300

Temperature (K) (10

⁵

V/cm) (10

⁵

V/cm) (10

⁵

V/cm)

80 2.32 2.38 2.46

120 2.41 2.43 2.51

150 2.43 2.47 2.55

180 2.49 2.51 2.61

210 2.52 2.56 2.64

240 2.57 2.59 2.68

270 2.61 2.64 2.72

300 2.66 2.72 2.78

Table 2. The parameters obtained from fitting procedure using Varshni equation.

Parameter α β E(0)

Sample (nm) (x10

⁻⁴

eV/K) (K) (eV)

70 6.81 427 1.350

150 6.35 412 1.347

300 5.89 405 1.345

s

7 £ x % i . Õ ª Q InGaAs 8 £ x _ ¿ ºa 300 nm{ 9 M

: ¿ º r « Ñ\ q K ì ø Í& h Ü ¼ Ð ß ¼> H X <, s H strain % ò ¾ Ós ¿ º r « Ñ\ q K ß ¼> l M :ë H s .

Fig. 4 H Fig. 3 _ \ x 8 £ x _ ¿ ºa 70, 150, 300 nm { 9 M

:_ InGaAs ½ × ¼Ì s \ -t _ : r ¸ _ > r$ í ` ¦ ? /% 3

. s Õ ªa Ë >\ " f z ´ É r Varshni ~ ½ Ó& ñ d

E g (T ) = E(0) − αT ² /(β + T ) (3)

`

¦ 6 x K " f x h A % i . s d \ " f E ^g (T ) ü < E(0) H y y

: r ¸ T x 9 0 K\ " f ½ × ¼Ì s \ -t \ ¦ ? / 9, α, β H y

y : r ¸ o\ É r \ -t s 1 l x ¸ x 9 ¨ î ç H : r ¸\ ¦

· p . 0 A_ d Ü ¼ Ð ½ ¨ô Ç InGaAs s \ -t \ @ /ô Ç α, β x 9 E(0)° ú כ[ þ t` ¦ Table 2 \ ? /% 3 .

IV. + s Ç Â ] Ø

¸\ " f_ InGaAs8 £ x _ ¿ ºa (70, 150, 300 nm)\ É r F

g : £ ¤$ í ` ¦ PRZ O Ü ¼ Ð ¸ % i . FKO ÐÂ Ò' ½ × ¼Ì s

\

-t \ ¦ ½ ¨ % i Ü ¼ 9, \ x 8 £ x In 0.1 Ga 0.9 As _ ¿ ºa

¿

º Ö ¦ Ã º2 ¤ strain % ò ¾ Ó` ¦ ´ ú §s ~ Ã Î ½ × ¼Ì s \ -t

$

\ -t Ð s 1 l x ÷ &% 3 . s H T. H. Chen 1 p x [13] s Al- GaAs/InGaAs/GaAs high electron mobility transistor ½ ¨

¸\ " f InGaAs8 £ x _ ¿ ºa _ 7 £ x \ 11H, 12H, 21H, 22H1 p x _ \ -t y è < Ê` ¦ Ð e . Õ ªo ¦ : r ¸

\

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Fig. 4. Temperature dependence of the In 0.1 Ga 0.9 As (70,150,300 nm) band gap energies of the PR.

a

\ 7 £ x % i Ü ¼ 9, Õ ªo ¦ s ° ú כ É r : r ¸ 7 £ x < Ê

\

Õ ª [ jl 7 £ x % i .

P

c p 8 ý ò k >

: r ½ ¨ H 2005¸ @ /½ ¨@ / < Æ § < ÆÕ ü t ½ ¨q { 9 Â Ò t " é ¶ Ü

¼ Ð Ã º' ÷ &% 3 _ þ v m .

[1] T. Mozume and N. Georgiev, Physica E 13, 361 (2002).

[2] T. Akiyama, et al., Electron. Lett. 37, 129 (2001).

[3] P. J. Hughes, B. L. Weiss and T. J. Hosea, J. Appl.

Phys. 77, 6472 (1995).

[4] S. Adachi, J. Appl. Phys. 61, 4869 (1987).

[5] M. Astles, et al., J. Electron. Mater. 15, 41 (1986).

[6] J. R. Chang, et al., Appl. Phys. Lett. 75, 238 (1999).

[7] S. Shirakata, M. Kondow and T. Kitatani, Appl.

Phys. Lett. 79, 54 (2001).

[8] A. Wo ˆ Ajs, P. Hawrylak, S. Fafard and L. Jacak, Phys. Rev. B 54, 5604 (1996).

[9] J. Misiewicz, K. Jezierski, P. Sitarek, P. Markiewicz, R. Korbutowicz, M. Panek, B. S ˆ Aciana and M.

Tlaczala, Adv. Mater. Opt. Electron. 5, 321 (1995).

[10] H. Lee, W. Yang and P. C. Sercel, Phys. Rev. B 55, 9757 (1997).

[11] F. H. Pollak and M. Balkanski, Handbook on Semi- conductors, (North Holland, Amsterdam, 1994), p.

527. [12] J. I. Yu, S. J. Lee, K. H. Kim, I. H. Bae, J. S. Son and D. N. Kim, New Phys. 49, 289 (2004).

[13] T. H. Chena, Y. S. Huanga; T. S. Shoub, K.

K. Tiongb, D. Y. Linc, F. H. Pollakd and M. S.

Goorskye, D. C. Streitf , M. Wojtowiczf. Physica. E

8, 297 (2000).

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Photoreflectance Characteristics of GaAs/In _0.1 Ga _0.9 As/GaAs Structures

Jae-In Yu, Hun-Bo Park and In-Ho Bae ^∗

Department of Physics, Yeungnam University, Gyeongsan 712-749 Sung Bae Park

Department of Physics, Daegu University, Gyeongsan 712-714 (Received 13 February 2006)

We have studied the photoreflectance (PR) of GaAs/In

0.1

Ga

0.9

As/GaAs heterostructures with different thicknesses of InGaAs layers grown by using metal-organic chemical-vapor deposition (MOCVD). The room-temperature PR spectra show two typical signals, around 1.42 and 1.30 eV, which can be attributed to the band gap energies of GaAs and InGaAs, respectively. In addition, we observe Franz-Keldysh oscillations above the InGaAs fundamental band gap. From these oscil- lations, we calculate the electric fields at the In

0.1

Ga

0.9

As/GaAs interface. Also, the temperature dependence of the PR peak is investigated.

PACS numbers: 78

Keywords: Photoreflectance, FKO, InGaAs, Electric field

∗

E-mail: [email protected]

GaAs/In 0.1 Ga 0.9 As/GaAs   º; c" e8 ý Photoreflectance  ¤V R Ë  ì Å 

GaAs/In 0.1 Ga 0.9 As/GaAs   º; c" e8 ý Photoreflectance  ¤V R Ë  ì Å 

­

¤<  - > ·   g Y @ ¹ · 9  - >  Ú ∗

% ò

z  @ / < Æ § Ó ü t o  < Æõ ,  â í ß  712-749



 ) ç 9 

@

/½ ¨@ / < Æ § Ó ü t o  < Æõ ,  â í ß  712-714 (2006¸  2 Z 4 13{ 9  ~ Ã Î6 £ §)

MOCVD (metal organic chemical vapor deposition)  Ð $ í  ©   ) a GaAs/In

Ga

As/GaAs s 7 á x] X 

½

+ Ë ½ ¨ ¸\ " f InGaAs 8 £ x _  ¿ ºa \    É r F g : £ ¤$ í `  ¦ photoreflectance (PR) ~ ½ ÓZ O Ü ¼ Ð  ¸  % i  . Õ ªo 



¦  ©  : r PR Û ¼& 7 à Ô! 3 \ " f GaAs_   ½ × ¼Ì  s\   ' aº   ) a   ñ    1.42 eV\ " f  ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, Õ ªo  ¦ In

Ga

As \   ' a >   ) a   ñ  H ¿ ºa  70, 150 x 9 300 nm\  @ /K " f y  y   1.311, 1.296 x 9 1.287 eV\ 

"

f  ' a8 £ ¤ ÷ &% 3  .  ©  : r x 9 $  : r \ " f Franz-Keldysh oscillations (FKOs)s  In

Ga

As ü < GaAs  ½ × ¼ Ì

 s \  -t   s \ " f  ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, FKO_  Å Òl \  ¦ :  x K  In

Ga

As/GaAs _  >     l  ©  ° ú כ`  ¦ ½ ¨

% i  .

PACS numbers: 78

Keywords: F g ì ø Í , FKO, InGaAs, >     l  © 

I. " e Â ] Ø

þ

j   H \  In x Ga 1−x As/GaAs s 7 á x] X ½ + Ë ½ ¨ ¸\  æ ¼s   H l  ó

ø Í F « Ñ Ð  H GaAs l ó ø Í\  q K " f  ¦ s 1 l x  ¸\  ¦ t  ¦, Ô

 ¦í  HÓ ü t 0 l x  ¸ 50 % & ñ  ¸  8  H InP l ó ø Í`  ¦  6 x ô  Ç  [1-3]. t ë ß  InP  H GaAs \  q K      Ô  ¦{ 9 u   8 ß ¼ l

 M :ë  H \  In x Ga 1−x As \  p u   H   + þ A´ òõ   8 ß ¼>  { 9 

#

Qè ß  .   " f î ß & ñ & h    è \  ¦ ë ß [ þ t M :  H GaAs l ó ø Í

`

 ¦  6 x ô  Ç .  Ð:  x In x Ga 1−x As/GaAs s 7 á x] X ½ + Ë ½ ¨ ¸  H F

g  è   Y Us $  s  ¸× ¼ 1 p x \  ´ ú §s   6 x ) a  [4-6].

In x Ga 1−x As \ x 8 £ x É r  Ð:  x In _   ¸$ í q \      ½ × ¼Ì  s

\

 -t  Ø Ô . s  Qô  Ç F g  è \   6 x ÷ &  H F « Ñ\  F g :

£ ¤$ í ì  r$ 3 s  6 x s ô  Ç ~ ½ ÓZ O  É r    ¸ ì  rF gZ O  ×  æ \     photoreflectance (PR)  Å Ò Ð  6 x ) a . s  PRZ O  É r #  l

 F g Ü ¼ Ð  §À Ó+ þ AI _  é ß Ò  oF g 7 £ ¤, Y Us $ \  ¦ Å Ò Ð s 6 x 

#

 r « Ñ ? /Â Ò\     -& ñ / B N  ©  (electron-hole pair ; EHP)

`

 ¦ Ò q t$ í r v  ¦, Å Òl & h Ü ¼ Ð ³ ð    l  © `  ¦   or (  Ü ¼



Ð+  f  À Ó+ þ AI  Ð r « Ñ\  { 9    ) a y n C_  ì ø Í Ö  ¦ s \  ¦ 8 £ ¤

&

ñ   H  כ s  9, ì ø Í ¸^ _  ³ ð  , s 7 á x] X ½ + Ë ½ ¨ ¸_  >   ¢ ¸



 H \  -t  {  ½ ¨ ¸\  ¦  ¸    H X <  Å Ò Ä »6 x ô  Ç ~ ½ ÓZ O s   [7-9].  : r  7 Hë  H \ " f  H F K5 Å q Ä »l  l  ©  7 £ x  Ã Ì (metal organic

E-mail: [email protected]

chemical vapor deposition; MOCVD)Z O Ü ¼ Ð SI-GaAs l  ó

ø Í0 A\  In 0.1 Ga 0.9 As8 £ x (70, 150 x 9 300 nm)`  ¦ $ í  © r  

6 £ §, cap8 £ x Ü ¼ Ð Ô  ¦í  HÓ ü t`  ¦ '   t  · ú §  H GaAs8 £ x`  ¦ 150 nm`  ¦ $ í  © r &  GaAs/In 0.1 Ga 0.9 As/GaAs ½ ¨ ¸_  F g : £ ¤

$ í

`  ¦ PR ~ ½ ÓZ O Ü ¼ Ð  ¸  % i  .

II. ÷ m Ç ] M ö



: r   ½ ¨\   6 x ) a r « Ñ  H ì ø Í] X   $ í GaAs l ó ø Í 0 A\ 

!

Q( 8 £ x Ü ¼ Ð Ô  ¦í  HÓ ü t s  '   t  · ú § É r GaAs (i-GaAs)\  ¦ 300 nm`  ¦ $ í  © r   Ê ê, In 0.1 Ga 0.9 As \ x 8 £ x _  ¿ ºa \  ¦ 70, 150, 300 nm  Ð y  y   $ í  © r (   . Õ ªo  ¦ cap8 £ x Ü ¼



Ð Ô  ¦í  HÓ ü t s  '  ÷ &t  · ú §  H GaAs\  ¦ 150 nm $ í  © r   GaAs/In 0.1 Ga 0.9 As/GaAs ½ ¨ ¸\  ¦ ° ú   H 3 > h_  r « Ñ\  ¦   6

x % i  . s  z ´+ « >_  8 £ ¤& ñ  ¸|  É r pump beam Ü ¼ Ð He- Ne (632.8 nm) Y Us $ \  ¦  6 x % i  ¦, Å Ò Ã º  H F g é ß 5 Å q l

\  ¦  6 x #     ¸r (   . Õ ªo  ¦ F g " é ¶ Ü ¼ Ð  H 250 W _

 ) í Û ¼J $  ½ + É Ð  p Ï þ á Ô\  ¦  6 x % i Ü ¼ 9,  í& h  o  0.75 m  é ß Ò  o o  © u \  ¦ :  x #   : r probe F g`  ¦ r « Ñ\  { 9   r

&  s M : ì ø Í   ) a F g`  ¦ z ´o  B H F g   Ø  ¦ l  Ð   Ø  ¦ % i  .

F

g   Ø  ¦ l \ " f   Ø  ¦ ) a   ñ  H 7 £ x;  ¤ l  (pre-amplifier)\  ¦ :



x K  7 £ x;  ¤ Ê ê, lock-in amplifier Ð ½ ©  o  ) a    ¸ ì ø Í Ö  ¦

-420-

Fig. 1. Photoreflectance spectra of three GaAs/In 0.1 Ga

0.9 As/GaAs heterostructures for various thicknesses of the In 0.1 Ga 0.9 As epilayer.

(∆R/R)`  ¦ ½ ¨ô  Ç Ê ê PC Ð :  x K  Û ¼& 7 à Ô! 3 Ü ¼ Ð  ? /% 3 

GaAs/In 0.1 Ga 0.9 As/GaAs º; c" e8 ý Photoreflectance ¤V R Ë ì Å

GaAs/In 0.1 Ga 0.9 As/GaAs º; c" e8 ý Photoreflectance ¤V R Ë ì Å

¤< - > · g Y @ ¹ · 9 - > Ú ^∗

z @ / < Æ § Ó ü t o < Æõ , â í ß 712-749

) ç 9

/½ ¨@ / < Æ § Ó ü t o < Æõ , â í ß 712-714 (2006¸ 2 Z 4 13{ 9 ~ Ã Î6 £ §)

MOCVD (metal organic chemical vapor deposition) Ð $ í © ) a GaAs/In

As/GaAs s 7 á x] X

+ Ë ½ ¨ ¸\ " f InGaAs 8 £ x _ ¿ ºa \ É r F g : £ ¤$ í ` ¦ photoreflectance (PR) ~ ½ ÓZ O Ü ¼ Ð ¸ % i . Õ ªo

¦ © : r PR Û ¼& 7 à Ô! 3 \ " f GaAs_ ½ × ¼Ì s\ ' aº ) a ñ 1.42 eV\ " f ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, Õ ªo ¦ In

As \ ' a > ) a ñ H ¿ ºa 70, 150 x 9 300 nm\ @ /K " f y y 1.311, 1.296 x 9 1.287 eV\

f ' a8 £ ¤ ÷ &% 3 . © : r x 9 $ : r \ " f Franz-Keldysh oscillations (FKOs)s In

As ü < GaAs ½ × ¼ Ì

s \ -t s \ " f ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, FKO_ Å Òl \ ¦ : x K In

As/GaAs _ > l © ° ú כ` ¦ ½ ¨

% i .

Keywords: F g ì ø Í , FKO, InGaAs, > l ©

j H \ In ^x Ga 1−x As/GaAs s 7 á x] X ½ + Ë ½ ¨ ¸\ æ ¼s H l ó

ø Í F « Ñ Ð H GaAs l ó ø Í\ q K " f ¦ s 1 l x ¸\ ¦ t ¦, Ô

¦í HÓ ü t 0 l x ¸ 50 % & ñ ¸ 8 H InP l ó ø Í` ¦ 6 x ô Ç [1-3]. t ë ß InP H GaAs \ q K Ô ¦{ 9 u 8 ß ¼ l

M :ë H \ In x Ga _1−x As \ p u H + þ A´ òõ 8 ß ¼> { 9

Qè ß . " f î ß & ñ & h è \ ¦ ë ß [ þ t M : H GaAs l ó ø Í

¦ 6 x ô Ç . Ð: x In x Ga _1−x As/GaAs s 7 á x] X ½ + Ë ½ ¨ ¸ H F

g è Y Us $ s ¸× ¼ 1 p x \ ´ ú §s 6 x ) a [4-6].

In _x Ga _1−x As \ x 8 £ x É r Ð: x In _ ¸$ í q \ ½ × ¼Ì s

-t Ø Ô . s Qô Ç F g è \ 6 x ÷ & H F « Ñ\ F g :

£ ¤$ í ì r$ 3 s 6 x s ô Ç ~ ½ ÓZ O É r ¸ ì rF gZ O × æ \ photoreflectance (PR) Å Ò Ð 6 x ) a . s PRZ O É r # l

F g Ü ¼ Ð §À Ó+ þ AI _ é ß Ò oF g 7 £ ¤, Y Us $ \ ¦ Å Ò Ð s 6 x

r « Ñ ? /Â Ò\ -& ñ / B N © (electron-hole pair ; EHP)

¦ Ò q t$ í r v ¦, Å Òl & h Ü ¼ Ð ³ ð l © ` ¦ or ( Ü ¼

Ð+ f À Ó+ þ AI Ð r « Ñ\ { 9 ) a y n C_ ì ø Í Ö ¦ s \ ¦ 8 £ ¤

ñ H כ s 9, ì ø Í ¸^ _ ³ ð , s 7 á x] X ½ + Ë ½ ¨ ¸_ > ¢ ¸

H \ -t { ½ ¨ ¸\ ¦ ¸ H X < Å Ò Ä »6 x ô Ç ~ ½ ÓZ O s [7-9]. : r 7 Hë H \ " f H F K5 Å q Ä »l l © 7 £ x Ã Ì (metal organic

chemical vapor deposition; MOCVD)Z O Ü ¼ Ð SI-GaAs l ó

ø Í0 A\ In ^0.1 Ga 0.9 As8 £ x (70, 150 x 9 300 nm)` ¦ $ í © r

6 £ §, cap8 £ x Ü ¼ Ð Ô ¦í HÓ ü t` ¦ ' t · ú § H GaAs8 £ x` ¦ 150 nm` ¦ $ í © r & GaAs/In 0.1 Ga _0.9 As/GaAs ½ ¨ ¸_ F g : £ ¤

` ¦ PR ~ ½ ÓZ O Ü ¼ Ð ¸ % i .

: r ½ ¨\ 6 x ) a r « Ñ H ì ø Í] X $ í GaAs l ó ø Í 0 A\

Q( 8 £ x Ü ¼ Ð Ô ¦í HÓ ü t s ' t · ú § É r GaAs (i-GaAs)\ ¦ 300 nm` ¦ $ í © r Ê ê, In ^0.1 Ga 0.9 As \ x 8 £ x _ ¿ ºa \ ¦ 70, 150, 300 nm Ð y y $ í © r ( . Õ ªo ¦ cap8 £ x Ü ¼

Ð Ô ¦í HÓ ü t s ' ÷ &t · ú § H GaAs\ ¦ 150 nm $ í © r GaAs/In _0.1 Ga _0.9 As/GaAs ½ ¨ ¸\ ¦ ° ú H 3 > h_ r « Ñ\ ¦ 6

x % i . s z ´+ « >_ 8 £ ¤& ñ ¸| É r pump beam Ü ¼ Ð He- Ne (632.8 nm) Y Us $ \ ¦ 6 x % i ¦, Å Ò Ã º H F g é ß 5 Å q l

\ ¦ 6 x # ¸r ( . Õ ªo ¦ F g " é ¶ Ü ¼ Ð H 250 W _

) í Û ¼J $ ½ + É Ð p Ï þ á Ô\ ¦ 6 x % i Ü ¼ 9, í& h o 0.75 m é ß Ò o o © u \ ¦ : x # : r probe F g` ¦ r « Ñ\ { 9 r

& s M : ì ø Í ) a F g` ¦ z ´o B H F g Ø ¦ l Ð Ø ¦ % i .

g Ø ¦ l \ " f Ø ¦ ) a ñ H 7 £ x; ¤ l (pre-amplifier)\ ¦ :

x K 7 £ x; ¤ Ê ê, lock-in amplifier Ð ½ © o ) a ¸ ì ø Í Ö ¦

Fig. 1. Photoreflectance spectra of three GaAs/In _0.1 Ga

0.9 As/GaAs heterostructures for various thicknesses of the In _0.1 Ga _0.9 As epilayer.

(∆R/R)` ¦ ½ ¨ô Ç Ê ê PC Ð : x K Û ¼& 7 à Ô! 3 Ü ¼ Ð ? /% 3

.

Fig. 1 É r 300 K \ " f 8 £ ¤& ñ ô Ç GaAs/In _0.1 Ga _0.9 As/GaAs

¨ ¸_ PR Û ¼& 7 à Ô s . s Õ ªa Ë >\ " f 1.42 x 9 1.30 eV

" f ' a8 £ ¤ ) a ñ H y y GaAs x 9 In 0.1 Ga 0.9 As _ { ç ß

\ -t s . Õ ªo ¦ In ^0.1 Ga 0.9 As ü < GaAs_ > s

\ { 9 & ñ ô Ç Å Òl \ ¦ t H 1 l x[ þ t (OS region) s ¸ H r

« Ñ\ " f ' a8 £ ¤ ÷ &% 3 H X <, s H Franz-Keldysh oscillations (FKOs) ´ òõ s .

¦ l © % ò % i _ PR ñ\ " f ' a8 £ ¤ ÷ & H FKO ÐÂ Ò'

½ × ¼Ì s \ -t H 6 £ §d Ü ¼ Ð ³ ð & ³ ) a [10-12].

E _j = ~ΩF j + E _g (1) F _j = [ 3π

l " f E j H FKO _ j P : x ß ¼ \ -t s ¦, E g H ½

¼Ì s \ -t s . Õ ªo ¦ Ã º ~Ω É r 6 £ §d Ü ¼ Ð ³ ð & ³ ) a

.

~Ω = ( e ² ~ ² E ²

d

(2)\ " f e H _ , µ H ü < Á º î r & ñ / B N

@ /ô Ç ¨ 8 í ß | 9 | ¾ Ó, Õ ªo ¦ E H l © s . F j \ É r E j _ Õ ªA á Ô\ " f f õ E j » ¡ ¤ õ _ §& h É r E g s ¦, Õ ªa Ë >

l Ö ¦ l ÐÂ Ò' d (2)\ ¦ 6 x # l © ` ¦ ½ ¨½ + ÉÃ º e

. InGaAs ¿ ºa 70, 150 x 9 300 nm\ @ /ô Ç ½ × ¼Ì s \

-t \ ¦ ½ ¨ô Ç õ y y 1.311, 1.296, 1.287 eV % i Ü ¼ 9, InGaAs ¿ ºa 7 £ x ½ + É Ã º2 ¤ ½ × ¼Ì s \ -t y è % i

. s H ¿ ºa ¿ º Ö ¦ Ã º2 ¤ strain % ò ¾ Ós & t l M :ë H s

. Õ ª Q [ j r « Ñ ¸¿ º PR Û ¼& 7 à Ô \ " f InGaAs

ñ ¸ ú ' a8 £ ¤ ÷ &% 3 l M :ë H \ , InGaAs \ x 8 £ x É r e > ¿ ºa

A \ $ í © ÷ &% 3 ¦ ½ + É Ã º e . Fig. 2 H y r « Ñ\ @ / ô

Ç F j \ @ /ô Ç E j ü <_ ' a > \ ¦ ? /% 3 . s Õ ªa Ë >_ l Ö

¦ l ÐÂ Ò' 300 K\ " f l © É r InGaAs r « Ñ_ ¿ ºa

70, 150 x 9 300 nm\ @ /K " f y y 2.66 × 10 ⁵ , 2.72 × 10 ⁵ Õ

ªo ¦ 2.78 × 10 ⁵ V/cm s % 3 .

Fig. 3(a),(b) x 9 (c) H y r « Ñ_ : r ¸ _ > r$ í \ @ /ô Ç PR Û ¼& 7 à Ô s . Õ ªa Ë >\ " f : r ü < ° ú s PR ñ_ + þ A I

H ¸ H r « Ñ\ @ /K _ Ä » ô Ç â ¾ Ó` ¦ Ð% i Ü ¼ 9, InGaAs x 9 GaAs\ ' aº ) a ñ H : r ¸ 7 £ x ½ + É Ã º2 ¤

¦ \ -t Ð s 1 l x ÷ &% 3 . s H & ñ Ø ½ Ó H d Ü ¼ Ð