In x Ga 1 −x As/GaAs ú n Þ W ë s ¤ ö n Ú º8 ý ° Ë Ñ] K ¡X ì Ä ¤V R Ë ì Å
¤< - > · Ðg ` @* > · »M ý ¡ · 9 - > Ú ∗
% ò
z @ / < Æ § Ó ü t o < Æõ , â í ß 712-749
T
ò 6 BZ Ì
LG z ´à Ô : r ½ ¨ è, ½ ¨p 730-350 (2004¸ 6 Z 4 8{ 9 ~ Ã Î6 £ §)
l
ó ø Ís É r ¿ º 7 á x À Ó\ $ í © ) a InGaAs/GaAs × æ ª Ä ºÓ ü t(MQW)_ F g < Æ& h : £ ¤f ç ` ¦ ¸ , ì r$ 3
% i . 2
◦-off ) a GaAs l ó ø Í\ $ í © ô Ç × æ ª Ä ºÓ ü t_ In_ ¸$ í q H 0.06 s ¦, exact GaAs l ó ø Í\
$ í
© ô Ç ª Ä ºÓ ü t_ ¸$ í q H 0.08 s 9, s ¿ º 7 á x À Ó_ Ä ºÓ ü t ¿ ºa H y y 2, 4, 6 nms . 8 £ ¤& ñ ) a PL x ß
¼_ ì ø Íu ; ¤(FWHM) s 2
◦-off GaAs_ â Ä º\ e # Q" f H 12 meV % i Ü ¼ 9, ì ø Í \ exact GaAs â Ä
º\ H 32.3 meV Ð peak broadenings 2
◦-off ) a r « Ñ Ð ß ¼> z ¤ . s H 2
◦-off GaAs_ â Ä
º Ð & ñ $ í s b # Qt Ù ¼ Ð K " f µ 1 ÏF g ´ òÖ ¦ s ± ú t l M :ë H s .
PACS numbers: 78
Keywords: F g ì ø Í , F g ~ ½ ÓØ ¦, × æ ª Ä ºÓ ü t
I. " e  ] Ø
þ
j H t 1.3 ∼ 1.5 µm @ /_ © ` ¦ t H Y Us $ [ þ t
É
r F g$ 3 Ä » : x l Õ ü t_ µ 1 ϲ ú Ð F g# 3 0 A > ½ ¨÷ &# Q M ® o
[1]. Stranski-Krastanow(S-K) ~ ½ ÓZ O ` ¦ 6 x # $ í © r
self-assembled quantum dots(QDs) É r ì ø Í ¸^ è [
þ
t` ¦ ] j H X < × æ כ ¹ô Ç F « Ñs [1]. QDs` ¦ ë ß [ þ t M :, InAs QD 0 A\ strain-reduced layers(SRLs)Ü ¼ Ð InGaAs 8
£
x` ¦ 6 xô Ç . AlGaAs 8 £ x ¸ 6 x ÷ &t ë ß , © @ /& h Ü ¼ Ð
+ þ A` ¦ & h > ~ Ã Î H InGaAs 8 £ x s ì ø Í ¸^ è ] j \ Ã º כ
¹ 8 ß ¼ . InGaAs 8 £ x É r F g è _ F « Ñ Ð ´ ú §s > h µ
1 Ï÷ &# Q M ® o ¦, þ j H \ H QDs Y Us $ ü < ª Ä ºÓ ü t Y Us $ ü
< ° ú É r ¦l 0 p x_ è \ ¦ > hµ 1 Ï H X < Ä »6 x > s 6 x ÷ &
¦ e [2, 3]. { 9 ì ø Í& h Ü ¼ Ð è _ Ó ü t o & h : £ ¤$ í É r ª | 9 _ l ó ø Íõ $ í © ÷ & H 8 £ x_ & ñ $ í & ñ ¸\ ß ¼> % ò ¾ Ó` ¦
~ Ã
Î H . InGaAs/GaAsü < ° ú É r s 7 á x] X ½ + Ë ½ ¨ ¸_ ì ø Í ¸^
\
" f H l ó ø Í_ © à ºü < É r © à º\ ¦ t ¦ e
H Ó ü t| 9 ` ¦ ª | 9 _ \ x 8 £ x Ü ¼ Ð $ í © r ~ ´ M : H ´ ú § É r ] j s
Ø Ô> ÷ & 9, $ í © ÷ & H 8 £ x_ & ñ $ í É r \ x 8 £ x_ ¸
$ í
õ ¿ ºa \ % ò ¾ Ó` ¦ ~ Ã Î> ) a . ¢ ¸ô Ç, Â Ò& ñ ½ + Ë & ñ ¸ ß ¼
>
H Ó ü t| 9 \ e # Q" f, ¿ ºa o\ " f
H s ¢ - a r \ $ í © ) a \ x 8 £ x_ ½ ¨ ¸& h o 1 l x
∗
E-mail: [email protected]
r
\ { 9 # Qè ß . \ x 8 £ x_ ½ ¨ ¸& h oü < & ñ $ í ` ¦ ¾ Ó © r
v l 0 Aô Ç ½ ¨[ þ t s s 7 á x] X ½ + Ë ½ ¨ ¸\ ¦ ô Ç ì ø Í ¸^ Ó ü t| 9 [
þ
t \ @ /K " f ´ ú §s ' ÷ &# Q M ® o [4, 5]. : r ½ ¨\ " f H molecular beam epitaxy(MBE)Z O ` ¦ 6 x # ~ ½ Ó ¾ Ós
É
r l ó ø Í 0 A\ InGaAs/GaAs × æ ª Ä ºÓ ü t ½ ¨ ¸_ Ä º Ó
ü
t 8 £ x_ ¿ ºa \ ¦ Ø Ô> $ í © # photoreflectance(PR) ü
< photo-luminescence(PL) ~ ½ ÓZ O Ü ¼ Ð F g < Æ& h : £ ¤$ í ` ¦ ¸
% i .
II. T Â ] Ø
\
x 8 £ x_ $ í © s [001] ~ ½ Ó ¾ ÓÜ ¼ Ð ÷ &# Qe , In x Ga 1 −x As 8 £ x É r GaAs ü <_ © Ã º s Ð K 6 £ x§ 4 ` ¦
~
à Î> ) a . { 9 ì ø Í& h Ü ¼ Ð ì ø Í ¸^ Ó ü t| 9 [ þ t É r 1 p x~ ½ Ó$ í _ ò ø Í$ í
+ þ A` ¦ > ÷ &Ù ¼ Ð In x Ga 1 −x As ? /_ + þ A É r 6 £ § õ ° ú
[6].
⊥ r = (a ⊥ L − a r )/a r
ν r = (a ν L − a r )/a r (1)
#
l " f ⊥ r ü < ν r H [001] x 9 [100] ~ ½ Ó ¾ Ó\ " f_ + þ A§ 4 ` ¦ y y
· p . a ⊥ L ü < a ν L H y y In x Ga 1 −x As 8 £ x_ $ í © ~ ½ Ó
¾ Ó [001] ~ ½ Ó ¾ ÓÜ ¼ Ð_ © à ºü < ~ ½ Ó ¾ Ó [100] ~ ½ Ó ¾ Ó
-175-
Layer/Barrier Structure Composition Substrate
thickness (nm) 2/13 0.06 2
◦-off 4/13 In
xGa
1−xAs/GaAs GaAs 8/13 MQW (20 periods) Exact 2/10 0.08 GaAs 4/10 8/10
Table 2. Comparison between calculation and PL measurement for peak position of e1-hh1 transition of In x Ga 1 −x As/GaAs MQWs.
2 nm 4 nm 6 nm PL
Measurement (meV) 1502 ± 5 1491 ± 5 1479 ± 5 Calculation (meV) 1502 ± 5 1489 ± 5 1478 ± 5 Band offset 0.6 ± 0.1 0.75 ± 0.1 0.75 ± 0.1
_
© à º\ ¦ _ p ô Ç . ò ø Í$ í + þ A\ _ ô Ç ½ × ¼Ì s E g s H
6 £ § õ ° ú s ³ ð & ³ ) a .
E g s = E C o + ∆E C + ∆ V (2)
#
l " f, E C o H ò ø Í$ í + þ A` ¦ ~ Ã Ît · ú § ¤` ¦ M :_ ¸@ /_ \
-t ï r0 A Ð+ , ½ × ¼ ½ ¨ ¸\ ¦ & ñ H X < l ï r s ÷ & H כ Ü
¼ Ð Õ ª ° ú כ É r O Ü ¼ Ð ¦& ñ ô Ç . Õ ªo ¦ ∆E C H Ó ü t& ñ % i < Æ
+ þ A(hydrostatic deformation)\ _ ô Ç ¸@ /_ ½ × ¼é ß _ s 1 l x` ¦ _ p 9, ∆ V H ¸@ /\ ¦ l ï r Ü ¼ Ð 6 £ x§ 4 \ _ K o H @ /_ o ß ¼l \ ¦ · p .
III. ÷ m Ç ] M ö
ª | 9 _ \ x 8 £ x_ $ í © ` ¦ 0 AK : r ½ ¨\ " f H MBE (River 32P)Z O ` ¦ 6 x % i . l ó ø ÍÜ ¼ Ð 6 x ) a GaAs H etch pit density(EPD) ∼ 1500/cm 2 Ü ¼ Ð ¸ H l ó ø Ís epi-ready © I ª | 9 _ l ó ø Í` ¦ s 6 x % i . l ó ø Í_
&
ñ < Æ& h ~ ½ Ó ¾ Ó\ É r \ x 8 £ x_ F g < Æ& h : £ ¤$ í _ o\ ¦ ¶ ú (
R Ðl 0 AK (001) s ³ ð \ ¨ î ' ô Ç l ó ø Íõ ³ ð \
@
/K 2 ◦ -off ) a l ó ø Í` ¦ 6 x % i . \ x 8 £ x_ $ í © \
620 ◦ C \ " f undopped GaAs buffer layer` ¦ 5000
˚ A & ñ ¸ $ í © % i . Table 1 É r : r ½ ¨\ ¦ 0 AK $ í © ô Ç multiple quantum wells(MQWs)_ ½ ¨ ¸\ ¦ ç ß é ß >
? /% 3 .
Fig. 1 É r 2 -off ) a GaAs ü < exact GaAs l ó ø Í 0 A\ $ í
© ) a Ä ºÓ ü t8 £ x_ ¿ ºa 4 nm MQW\ @ /ô Ç PL Û ¼& 7 à
Ô \ ¦ Ð# Å Ò ¦ e . Fig. 1\ " f ^ ¦ Ã º e 1 p w s ¿ º r
«
Ñ\ " f ' a8 £ ¤ ) a x ß ¼ H ' Í P : ¸@ /_ \ " f ' Í P
: @ /_ Á º î r & ñ / B N s _ s (el-hh1)\ ' aº
)
a x ß ¼ Ð+ , H" é ¶ É r ° ú Ü ¼ \ -t s \ ¦ Ðs ¦ e
. 2 ◦ -off ) a GaAs_ â Ä º\ e # Q" f H 1.505 eVs % 3 t ë
ß , exact GaAs â Ä º\ e # Q" f H 1.49 eV & ñ ¸ Ð ¸y 9
É r \ -t Ð ' a8 £ ¤ ÷ &% 3 . s H 2 ◦ -off ) a GaAs ecact GaAs Ð + þ A§ 4 ` ¦ 8 ~ Ã Îl M :ë H Ü ¼ Ð « Ñ ) a . ¢ ¸ô Ç, PL x ß ¼_ ì ø Íu ; ¤ s 2 ◦ -off GaAs_ â Ä º\ e # Q" f H 12 meV & ñ ¸% i . s כ É r MQWs` ¦ + þ A$ í ¦ e H 8 £ x _
& ñ $ í s © { © y ª ñ H כ ` ¦ _ p ô Ç . Õ ª Q exact GaAs â Ä º\ H 32.3 meV Ð peak broadenings 2 ◦ -off ) a r « Ñ Ð ß ¼> z ¤ . s H 2 ◦ -off GaAs_
â
Ä º Ð & ñ $ í s b # Qt Ù ¼ Ð K " f µ 1 ÏF g ´ òÖ ¦ s ± ú t
H כ Ü ¼ Ð « Ñ ) a .
Fig. 2 H 15 K \ " f 2 ◦ -off GaAs l ó ø Í\ $ í © ) a MQWs_ Ä ºÓ ü t8 £ x ¿ ºa (2, 4, 6 nm)\ É r PL ñ[ þ t s
. y y \ @ /ô Ç x ß ¼_ 0 Au H 1989¸ D. J. Arent [7]
1 p
x s > í ß ô Ç ~ ½ ÓZ O Ü ¼ Ð % 3 # Q el-hh1 s ü < ¸ ú { 9 u < Ê
`
¦ · ú Ã º e Ü ¼ 9, Table 2\ ? /% 3 .
{ 9
ì ø Í& h Ü ¼ Ð, In 0.06 Ga 0.94 As (x ≥ 0.12) â Ä º\ e # Q Ä
ºÓ ü t8 £ x_ ; ¤ s © { © y a % v` ¦ â Ä º " l or : r ½ + Ë \ -t
Fig. 1. PL signals from InGaAs/GaAs MQWs for various
substrates.
Fig. 2. PL signals for various well width of In 0.06 Ga 0.94 As/GaAs MQWs.
10 meV & ñ ¸ Ð · ú 9t ¦ e [8]. Table 2\ " f Ðs
H כ É r PL ñ_ 0 Au ü < > í ß s _ s t
· ú § ¦ e . s כ É r z ´+ « > © u _ & ñ S X ô Ç C \ P _ & ñ ¸ü <
s \ -t > í ß r 9 כ ¹ô Ç parameter_ s 6 x \ " f
±
ú Ã º e H ¸ Ð # t , © { © y ¸ ú { 9 u % i . ¢ ¸
Fig. 3. Temperature dependence of PL signals for In 0.06 Ga 0.94 As/GaAs MQWs with 2 nm well width.
Fig. 4. Variation of el-hh1 transition energies for In 0.06 Ga 0.94 As/GaAs MQWs as a function of temper- ature.
ô
Ç, ¸@ /_ ½ × ¼ offsets Ä ºÓ ü t8 £ x_ ¿ ºa \ Ø Ô
>
¦ e Ü ¼ 9, 2 nm_ ¿ ºa \ ¦ t H r « Ñ s ü @\
"
f ¸@ /_ ½ × ¼ offset É r 0.75 H d` ¦ · ú Ã º e .
Fig. 3 É r Ä ºÓ ü t8 £ x_ ¿ ºa 2 nm MQW\ @ /ô Ç PL _
: r ¸ _ > r$ í ` ¦ · p . Fig. 3\ " f ^ ¦ Ã º e 1 p w s 8 £ ¤
Fig. 5. PR signals of In 0.06 Ga 0.94 As/GaAs MQWs for
various well widths.
\ ½ × ¼Ì s \ -t y è l M :ë H s .
Fig. 4 H Ä ºÓ ü t8 £ x_ ¿ ºa y y 2, 4, 6 nm â Ä º\
@
/ô Ç e1-hh1 s _ : r ¸\ É r x ß ¼ s 1 l x` ¦ ? / ¦ e
. Ä ºÓ ü t8 £ x_ ¿ ºa É r X < ¸ : r ¸_ 7 £ x \ s
\ -t _ y è â ¾ Ós ° ú . " f, QW\ _ ô Ç s
s ü @_ Ô ¦í HÓ ü t s < Ê\ _ ô Ç s H ' a8 £ ¤ ÷ &t · ú §
¤ .
Fig. 5 H 2 ◦ -off GaAs l ó ø Í\ $ í © ô Ç In 0.06 Ga 0.94 As/
GaAs MQWs \ @ /ô Ç © : r \ " f_ PR Û ¼& 7 à Ô! 3 [ þ t s .
¸ H r « Ñ[ þ t \ @ /K " f ñ_ ß ¼l ß ¼> z ` ¦ ^ ¦ Ã
º e Ü ¼ 9, broadenings É r ª ñô Ç ñ[ þ t` ¦ ' a8 £ ¤½ + É Ã
º e % 3 . Fig. 5\ " f Aü < C H y y © : r \ " f_ heavy hole õ light hole_ s \ ' aº ) a x ß ¼s . ¢ ¸ô Ç, Bü <
C s \ " f GaAs © # 4 _ ½ × ¼Ì s Ð Z } É r \ -t % ò % i
\
" f S X ÷ &t · ú § É r ñ[ þ t s ' a8 £ ¤ ÷ & ¦ e . Pan [9] 1 p x
\
_ s Qô Ç x ß ¼[ þ t É r 10 nm_ © # 4 8 £ x_ ; ¤` ¦
t H MQWs ? /\ " f coupling effect\ _ K Ä ºÓ ü t8 £ x_
×
æ © õ edge  Òì r \ " f_ s Æ Ò÷ &# Q l M : ë
H s [9,10].
V. + s Ç Â ] Ø
In x Ga 1 −x As/GaAs MQWs \ @ /ô Ç F g < Æ& h : £ ¤$ í ` ¦ PL x 9
PR ~ ½ ÓZ O Ü ¼ Ð ¸ ô Ç õ H 6 £ § õ ° ú .
1. × æ ª Ä ºÓ ü t ½ ¨ ¸\ " f e1-hh1 s H 2 ◦ -off GaAs ü < exact GaAs\ " f y y 1.505 x 9 1.49 eV\
"
f ' a8 £ ¤ ÷ &% 3 Ü ¼ 9, s x ß ¼ H Arent [7] 1 p x s > í ß ô Ç
~
½ ÓZ O Ü ¼ Ð ½ ¨ô Ç ° ú כõ ¸ ú { 9 u % i .
9, ¿ º r « Ñ× æ 2 ◦ -off GaAs \ $ í © ô Ç MQW_ r « Ñ
& ñ $ í s 8 Ä ºÃ º .
3. © : r PR Û ¼& 7 à Ô! 3 \ e # Q" f e1-hh1õ e1-lh1 s ü @ _
s x ß ¼[ þ t s GaAs ½ × ¼Ì s Ð Z } É r \ -t
\
" f ' a8 £ ¤ ÷ &% 3 . s H coupling effect \ l ) a כ s
.
Y c
p w à U Ø ô
[1] Wu. W, Tucker. J. R, Solomon. G. S and Harris. J.
S, Appl. Phys. Lett. 71, 1083 (1997).
[2] N. K. Dutta, J. Appl. Phys. 53, 7311 (1982).
[3] W. T. Tsang, Appl. Phys. Lett. 40, 217 (1982).
[4] N. G. Anderson, W. D. Laidig, R. M. Kolbas and Y.
C. Lo, J. Appl. Phys. 60, 2361 (1986).
[5] H. K. Dong, S. C. H. Hung and C. W. Tu, J. Elec- tron. Mater. 24, 327 (1995).
[6] T. P. Pearsall, F. H. Pollak, J. C. Bean and R. Hull, J. Vac. Sci. Technol. B 1, 338 (1983).
[7] D. J. Arent, K. Deneffe, C. Van Hoof, J. De Boeck and G. Borghs, J. Appl. Phys. 66, 1739 (1989).
[8] D. C. Reynolds, K. R. Evan. C. E. Stutz, B. Jogai, C. R. Wie and P. W. Yu, Amer. Phys. Soci. 45, 11156 (1992).
[9] H. Shen, S. H. Pan, Fred. H. Pllack and R. N. Sacks, Phys. Rev. B 37, 10919 (1988).
[10] D. N. Talwar, John. P. Loehr and B. Jogai, Phys.
Rev. B 49, 10345 (1994).
Photoluminescence and Photoreflectance Studies of In x Ga 1 −x As/GaAs Mutiple Quantum Wells
Jae-In Yu, Hyun-Min Cho, Ki-Hong Kim and In-Ho Bae ∗ Department of Physics, Yeungnam University, Kyoungsan 712-749
D. K. Lee
Research and Development Center, LG Siltron, Inc., Kumi 730-350 (Received 8 June 2004)
We have studied the structural and the optical properties of In
xGa
1−xAs/GaAs muliple quantum wells (MQWs) grown on two different substrates. The In compositions were x = 0.06 and 0.08 for the 2
◦-off (001) GaAs and the (001) GaAs substrates, respectively, and the thicknesses of the wells were 2, 4, and 6 nm. The calculated transition energies of the MQWs were consistent with those obtained from the Photoluminesecnce (PL) spectrum. The full wedths at half maximum (FWHMs) of the PL peaks were 12.5 and 32.3 meV for the 2
◦-off (001) GaAs and the (001) GaAs substrates, respectively. The weak PR peaks observed on the high - energy side of the GaAs barrier were attributed to the coupling effect.
PACS numbers: 78 Keywords: PR, PL, MQW
∗
