GaAsV ê s; c V R ËX ê sc Ü R Al 0.21 Ga 0.79 As/GaAs • «8 ý ì Å º Ä k È8 ý : gM ; c 6 ” X ¢ Photoreflectance — ¤V R Ë Ž ì ŏ Œ

 ƒ  ½ ¨ 7 Hë  H  Sae Mulli (The Korean Physical Society), Volume 58, Number 3, 2009¸   3 Z 4, pp. 392∼395

GaAsV ê s; c V R ËX ê sc Ü R Al ^0.21 Ga 0.79 As/GaAs • «8 ý
ì Å º Ä k È8 ý : gM ; c 6 ” X ¢ Photoreflectance — ¤V R Ë Ž ì ŏ Œ

­

¤<  - > ^∗ · 9  - > ‡ Ú

% ò

z Œ ™@ /† < Ɠ § Ó ü t o † < Æõ ,  â í ß – 712-749

(2008¸   10 Z 4 6{ 9  ~ à Î6 £ §, þ j7 á x‘ : r 2009¸   1 Z 4 29{ 9  ~ à Î6 £ §)

‘ :

r ƒ  ½ ¨\ " f  H Al

Ga

As/GaAs \  @ /ô  Ç  © œ“ : r photoreflectance (PR) _    › ¸c ”  [ jl \    É r F  g :

£ ¤$ í \  @ /K  › ¸  % i  .   › ¸ c ”  [ jl  7 £ x † < Ê\    , 1.49 ∼ 1.53 eV ½ ¨ç ß –\ " fPR Û ¼& 7 ˜à Ô _  … ô a _

 ß ¼l  7 £ x    H  ⠆ ¾ Ó`  ¦ › ' a ¹ 1 Ï % i  . „  l  © œ[ jl  & f ” \    É r % ò † ¾ ӓ    כ `  ¦ S X ‰ “  ½ + É Ã º e ” % 3  .

PACS numbers: 78.20.-e

Keywords: F  g ì ø Í ,  o½ + ËÓ ü t ì ø ͕ ¸^ ‰, „  l  © œ, F  g [ jl 

I. " e  ] Ø

3−57 á ¤  o½ + ËÓ ü t ì ø ͕ ¸^ ‰_  F  g : £ ¤$ í `  ¦ 8 £ ¤& ñ   H ~ ½ ÓZ O “ É r photoluminescence, x-ray, spectrometer 1 p x # Œ Q t  ~ ½ Ó Z O

s  e ”  . Photoreflectance (PR) Z O “ É r  o½ + ËÓ ü t ì ø ͕ ¸^ ‰ _

 s 7 á x] X ½ + ˽ ¨› ¸\ " f { ç ß –_  „  s  \  -t , ³ ð€   x 9  > €  

\

" f „  l  © œ_  ì  r Ÿ í 1 p x F  g † < Æ& h  : £ ¤$ í `  ¦ ¨ î    H X < ´ ú §s  s

6   x ÷ &  H ~ ½ ÓZ O s   [1–3]. PRZ O “ É r Y Us $  F  g \  _ K  Ò q t

$ í

 ) a ™ èà º H o # Q ³ ð€   © œI _  „   ü < F   ½ + ËÜ ¼– Ð “   ô

 Ç „  l  © œ_    › ¸\  _ ô  Ç  כ Ü ¼– Ð electroreflectance (ER)

\

 q K  $ “ : r õ  “ ¦“ : r \ " f_  s 6   x s  ˜ Ð  ¼ # o     H  © œ

&

h s  e ”  . s  Qô  Ç s Ä »– Ð r « Ñ ³ ð€  _  q ] X 8 ú ¤, q   õ 

&

h

 : £ ¤$ í Ü ¼– Ð ì ø ͕ ¸^ ‰_  p [ j½ ¨› ¸ 1 p x`  ¦ ƒ  ½ ¨   H X < 6   x s 

 9, ì ø ͕ ¸^ ‰_  Fermi ï  r 0 A_  0 Au \  ¦   & ñ “ ¦ F  g † < Æ& h Ü ¼

–

Ð ³ ð€   „   © œ`  ¦   & ñ ½ + É Ã º e ” Ü ¼Ù ¼– Ð z  ´] j ì ø ͕ ¸^ ‰ ™ è  ½ ¨

›

¸_  › ¸ \  e ” # Q" f Ä »6   x ô  Ç z  ´+ « >Z O s  ÷ &“ ¦ e ”  . PR ~ ½ Ó Z O

\ " f  H ×  æ כ ¹ô  Ç “    ” > r F    H X <, 7 £ ¤ „   @ /\ " f

„

 • ¸@ /– Ð # Œl  r v   H * 3 á Ôc ” _  % i ½ + És  . * 3 á Ôc ” “ É r ˜ Ð :

Ÿ

x r « Ñ t   H  ½ ™× ¼Ì “ s \  -t  s  © œ_  \  -t \  ¦ › ¸  r

†   . t ë ß – s  Qô  Ç ×  æ כ ¹ô  Ç % i ½ + É\ • ¸ Ô  ¦ ½ ¨ “ ¦ s \ 

@

/ô  Ç ƒ  ½ ¨  H  _  \ O   H z  ´& ñ s  .   " f ‘ : r ƒ  ½ ¨\ " f  H Al _0.21 Ga _0.79 As/GaAs s 7 á x] X ½ + ˽ ¨› ¸\ " f_  * 3 á Ô c ”  [ jl  7

£

¤   › ¸ c ”  [ jl \    É r r « Ñ : £ ¤$ í `  ¦ ƒ  ½ ¨ “ ¦  ô  Ç .

II. ÷ m Ç ] M ö

‘

: r ƒ  ½ ¨\   6   x ) a r « э  H ì ø Í] X ƒ  $ í GaAs l ó ø Í0 A\  molecular beam epitaxy (MBE)Z O \  _ K  Al 0.21 Ga _0.79 As

∗

E-mail: [email protected]

\

x 8 £ x`  ¦ 5000 ˚ A $ í  © œ r (   . z  ´+ « > ~ ½ ÓZ O “ É r PR 8 £ ¤& ñ `  ¦

% i  . Al 0.21 Ga _0.79 As/GaAs s 7 á x] X ½ + Ë ½ ¨› ¸_    › ¸ c ” 

\

 @ /ô  Ç _ ” > r$ í `  ¦ › ' a ¹ 1 Ï l  0 A # Œ   › ¸ c ”  [ jl \  ¦ 1 − 40 mW  t     or &  z  ´+ « >`  ¦ à º' Ÿ  % i  . PR 8 £ ¤& ñ “ É r



 › ¸ c ”  (pump beam)Ü ¼– Ð He-Ne laser (6328 ˚ A)\  ¦  6   x

% i Ü ¼ 9 probe beamÜ ¼– Ѝ  H 240 W ) í Û ¼J $ ™-½ + ɖ Ð
 p F  g " é ¶

`

 ¦  6   x % i  . y Œ •   © œZ >  é ß –Ò  oF  g`  ¦ % 3 l  0 AK   6   x ô  Ç ì  r F 

g l   H œ í& h  o  0.75 m“   l l  (Spex 750)\  ¦  6   x 

%

i  . Õ ªo “ ¦ — ¸Ž  H z  ´+ « >“ É r  © œ“ : r (300 K) \ " f à º' Ÿ  % i  .

Fig. 1. The PR spectrum of Al 0.21 Ga 0.79 As/GaAs in room temperature.

-392-

 ƒ  ½ ¨ 7 Hë  H  GaAs  © œ\  $ í  © œ  ) a Al

Ga

As/GaAs 8 £ x _ · · · – Ä »F “   · C “    ñ -393-

Fig. 2. The fitting graph of TDFF method in GaAs layer.

III. + s ÇÊ Ý õ m Í ‚ ºÂ ] Ø

Fig. 1“ É r Al 0.21 Ga _0.79 As/GaAs r « Ñ\  ¦ 300 K \ " f 8 £ ¤

&

ñ ô  Ç PR Û ¼& 7 ˜à Ô! 3 s  . s M :   › ¸ c ” _  [ jl   H 1 mW

%

i  . Õ ªa Ë >\ " f ˜ Ѝ  H  ü < ° ú  s  Å Ò  ) a ’    ñ ß ¼>  ¿ º > h

–

Ð
 
  H X <, 1.4 eV Â Ò   H \ " f
 
  H ’    ñ_    H" é ¶

“

É r GaAs \  _ ô  Ç ’    ñ– Ð · ú ˜ 94 R e ” “ ¦, 1.7 eV Â Ò   H \ " f

 è ß – ’    ñ  H Al 0.21 Ga 0.79 As \  _ ô  Ç ’    ñ– Ð · ú ˜ 94 R e ” 



.

Fig. 3. The dependence of modulation beam intensity in Al 0.21 Ga 0.79 As/GaAs sample.

s

 ¿ º ’    ñ_  & ñ S X ‰ ô  Ç  ½ ™× ¼Ì “ s \  -t \  ¦ · ú ˜ ? /l  0 A 

#

Œ Fig. 2(a), 2(b)\ " f ˜ Ѝ  H  ü < ° ú  s , third derivative function form (TDFF) – Ð x h A (fitting)ô  Ç   õ  GaAs  H 1.42 eV, Al 0.21 Ga 0.79 As  H 1.73 eV _   ½ ™× ¼Ì “ s \  -t \  ¦  t

  H  כ `  ¦ · ú ˜€ Œ ¤ . ˜ Ð: Ÿ x TDFF d ” “ É r  A d ”  (1)õ  ° ú  s 

³

ð‰ & ³ ) a   [4].

∆R

R (E) = Re[Ce ^iθ (E − E g + iΓ) ⁻ⁿ ] (1)

#

Œl " f C, θ, E ^g ü < Í  H y Œ •y Œ • ”  ; Ÿ ¤ (amplitude), 0 A



© œ (phase), e ” > & h \  -t  (critical point energy) x 9 

¨ î

ò ø ͓    (broadening parameter)\  ¦ o †   . Õ ªo “ ¦ Al _0.21 Ga _0.79 As \ x 8 £ x \ " f Al_  › ¸$ í q \  ¦ ½ ¨ l  0 A 

#

Œ  A  d ”  (2)\  ¦  6   x # Œ ½ ¨ô  Ç   õ  › ¸$ í q   H 21 % % i 



 [5–7].

E gAl

Ga

A

(x) = 1.424 + 1.427x + 0.041x ² (0 < x < 0.45) (2) Fig. 3“ É r   › ¸c ”  [ jl \    É r Al 0.21 Ga 0.79 As/GaAs r 

«

Ñ_  PR Û ¼& 7 ˜à Ô \  ¦
 ? /% 3  . Õ ªa Ë >\ " f  H ˜ Ѝ  H   ü

< ° ú  s    › ¸ c ”  [ jl  7 £ x ½ + Éà º2 Ÿ ¤ ’    ñ_  + þ AI   H   



o \ O   H ì ø ̀  \  ß ¼l   H & t   H X <, s   H   › ¸ c ” s  9 þ t Ã

º2 Ÿ ¤ ³ ð€  \ " f ? / Җ Ð S X ‰ í ß –÷ &  H „    ´ ú §l  M :ë  H s  .

¢

¸ô  Ç   › ¸ c ” _  [ jl \  ¦ 7 £ x r ( ” \     E o (GaAs) ü <

-394- ô  Dz D GÓ ü t o † < Æ rt  “D hÓ ü t o ”, Volume 58, Number 3, 2009¸   3 Z 4

Fig. 4. The graph of relationship beam intensity and amplitude.

E _o (Al _0.21 Ga _0.79 As) _  ’    ñ_  ß ¼l   H ‚  + þ A& h Ü ¼– Ð 7 £ x 

†

< Ê`  ¦ ˜ Ð# Œï  r  . s   H   › ¸ c ”  [ jl  (I)ü < ”  ; Ÿ ¤ ( ^∆R _R )  s  _

 › ' a >   A  d ”  (3)õ  ° ú  s  Å Ò# Qt l  M :ë  H s  .

∆R

R ∝ I

(3)

#

Œl " f ¹ n “ É r   › ¸ c ”  [ jl \  @ /ô  Ç ”  ; Ÿ ¤ õ _  › ' a > \ " f l  Ö

 ¦ l \  ¦
 ? /  H   à º– Ð" f e ” > & h  + þ AI \  ¦
  · p . Õ ª o

“ ¦ A ½ ¨ç ß – (1.49 ∼ 1.53 eV)\ " f ˜ Ðs   H … ô a_  ß ¼l 



 › ¸ c ” _  [ jl \     7 £ x ÷ &  H  ⠆ ¾ Ó`  ¦ ^  ¦ à º e ”  . s 



 H   › ¸ c ” _  [ jl  & | 9 à º2 Ÿ ¤ „   @ /\ " f „  • ¸@ /– Ð

#

Œl ÷ &  H „   _  à º  8 ´ ú §l  M :ë  H Ü ¼– Ð  « Ñ  ) a  . 7 £ ¤   

›

¸ c ” _  ß ¼l   H H o # Q 0 l x • ¸\  % ò † ¾ Ó`  ¦ Šғ ¦ s   H „  l  © œ _

 ß ¼l \  ¦ ß ¼>  K Šҍ  H % i ½ + É`  ¦ ô  Ç “ ¦ ½ + É Ã º e ”   [8–11].

Fig. 4  H   › ¸ c ”  [ jl  (I)ü < ”  ; Ÿ ¤ ( ^∆R _R )  s _  › ' a > \  ¦ Õ ª A

á Ԗ Ð
 ? /% 3 Ü ¼ 9, 0 A d ” `  ¦ t “ ¦ x h Aô  Ç   õ ü < ¸ ú ˜ { 9

u  % i   [12–14].

IV. + s Ç Â ] Ø

Al 0.21 Ga 0.79 As/GaAs \ x 8 £ x \  @ /ô  Ç PR 8 £ ¤& ñ `  ¦ : Ÿ x K 

% 3

“ É r Al 0.21 Ga 0.79 As x 9  GaAs_   ½ ™× ¼Ì “ s \  -t   H y Œ • y

Œ

• 1.42, 1.73 eV s % i  . ¢ ¸ô  Ç Al 0.21 Ga 0.79 As \  x

8 £ x _  Al › ¸$ í q \  ¦ ½ ¨ô  Ç   õ  21 %% i  . Õ ªo “ ¦ Al 0.21 Ga 0.79 As/GaAs _    › ¸ c ”  [ jl  _ ” > r$ í `  ¦ 8 £ ¤& ñ ô  Ç

 

õ , A ½ ¨ç ß – (1.49 ∼ 1.53 eV)\ " f ˜ Ðs   H … ô a_  ß ¼l 



 › ¸ c ” _  [ jl \     7 £ x ÷ &  H  ⠆ ¾ Ó`  ¦ ^  ¦ à º e ”  . s 



 H „  l  © œ_  ß ¼l  7 £ x  l  M :ë  H s  .

Y

c p w Š à U Ø ”  ô

[1] D. Y. Lin, Y. S. Huang, T. S. Shou, K. K. Tiong and Fred H. Pollak, J. Appl. Phys. 90, 6421 (2001).

[2] T. S. Moss, Photoconductivity in The Elements (Butterworths, London, 1952).

[3] B. Jogai, P. W. Yu and D. C. Streit, Appl. Phys.

Lett. 75, 1586 (1994).

[4] D. E. Aspence, Surf. Sci. 37, 418 (1973).

[5] J. Misiewicz, P. Sitarek and G. Sek, Opto-Electron.

Rev. 8, 1 (2000).

[6] M. De Vittorio, M. T. Todaro, V. Vitale, A. Pas- saseo, T. K. Johal, R. Rinaldi, R. Cingolani and S.

Bernardi, Microelectron. Eng. 61, 651 (2002).

[7] S. Adachi, J. Appl. Phys. 58, R1 (1985).

[8] P. Chen, Z. Miao and W. Lu, J. Cryst. Growth 227 - 228, 108 (2001).

[9] D. E. Aspnes and A. A. Studna, Phys. Rev. B 7, 4605 (1973).

[10] L. Zamora, A. Guill´ en, Z. Rivera, M. L´ opez, A. G.

Rodr´ıguez and V. H. M´ endez, Microelectron. J. 30, 521 (2003).

[11] J. Misiewicz, P. Sitarek and G. Sek, Opto-Electron.

Rev. 8, 1 (2000).

[12] Y. T. Oh, T. W. Kang and T. W. Kim, Thin Solid Films 265, 92 (1995).

[13] E. Estacio, M. Bailon, A. Somintac, R. Sarmiento and A. Salvador, J. Appl. Phys. 91, 3717 (2002).

[14] I. Hwang, J. E. Kim, H. Y. Park and S. K. Noh,

Solid State Commun. 103, 1 (1997).

 ƒ  ½ ¨ 7 Hë  H  GaAs  © œ\  $ í  © œ  ) a Al

Ga

As/GaAs 8 £ x _ · · · – Ä »F “   · C “    ñ -395-

The Study of the Photoreflectance Characteristics in Al _0.21 Ga _0.79 As grown on GaAs for a Variable Pumping Intensity

Jae-In Yu ^∗ and In-Ho Bae

Department of Physics, Yeungnam University, Gyeongsan 712-749 (Received 6 October 2008, in final form 29 January 2009)

We study of the photoreflectance characteristics of an Al

Ga

As/GaAs heterostructure.

We observed 1.49 ∼ 1.53 eV from the PR spectra for various pumping intensition. The room- temperature PR spectra exhibited A-region oscillations due to the increasing intensity of the electric field.

PACS numbers: 78.20.-e

Keywords: Photoreflectance, AlGaAs, Heterostructure

∗

E-mail: [email protected]