» ì Å ° Ë Ñ ¹ Å° q Ä Z Ø° Ë Ñ0 n É; c 8 ý X ¢ Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs ¥y ¢] k ù w

(1)

» ì Å ° Ë Ñ ¹ Å° q Ä Z Ø° Ë Ñ0 n É; c 8 ý X ¢ Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs ¥y ¢] k ù w

¹ Å T Ò Þy ¢ ² O U ' [ º8 ý ¤V R Ë

L

| ç ¡¬ £ · 9 - > Ú ^∗

% ò

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

»- > ¬ £

â

î r @ / < Æ § î ß â F g < Æõ , ½ ¨p 730-852

) ç 9

@

/½ ¨@ / < Æ § Ó ü t o < Æõ , â í ß 712-714

(2005¸ 5 Z 4 30{ 9 ~ Ã Î6 £ §, 2005¸ 8 Z 4 24{ 9 þ j7 á x : r ~ Ã Î6 £ §)

ì

r \ x × þ r (MBE) Z O Ü ¼ Ð $ í © ô Ç Al

0.24

Ga

0.76

As/In

0.2

Ga

0.8

As/GaAs Ã » ¸+ þ A ¦ s 1 l x ¸ à

Ô ½ t Û ¼' (p-HEMT) ½ ¨ ¸_ : £ ¤$ í ` ¦ ³ ð F g · ú ì rF gZ O (SPS)Ü ¼ Ð ½ ¨ % i . ³ ð F g · ú ñ

ÐÂ Ò' In

^0.2

Ga

0.8

As ª Ä ºÓ ü t ? /_ s [ þ t s × æ^ o ? ) a ñ Ð ' a8 £ ¤ ÷ &% 3 . s ñ\ ¦ ì r$ 3 l 0 AK , 1 p ì r+ þ A ³ ð F g · ú Û ¼& 7 à Ô! 3 ` ¦ x h A # & ñ S X ô Ç s \ -t _ 0 Au \ ¦ ½ ¨ % i . s õ [

þ

t É r s : r° ú כõ _ { 9 u % i .

PACS numbers: 71

Keywords: Al

0.24

Ga

0.76

As/In

0.2

Ga

0.8

As/GaAs Ã » ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' , ³ ð F g · ú ì rF gZ O , s

\

-t

I. " e Â ] Ø

Ã

» ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' (all pseudomorphic high electron mobility transistor; p-HEMT) ü < ° ú É r ¸

¸i ç ) a (modulation-doped) ½ ¨ ¸_ Ó ü t o & h : £ ¤$ í x 9 è 6

£

x6 x Ü ¼ Ð" f ´ ú § É r ½ ¨ ' ÷ &% 3 . : £ ¤ y , Al ^x Ga 1 −x As /In y Ga 1 −y As/GaAs ½ ¨ ¸ H Al x Ga 1 −x As/GaAs ½ ¨ ¸ü <

q

§ % i ` ¦ M : Z } É r Å Ò Ã º\ " f 8¹ ¡ ¤ ¾ Ó © ) a § 4 7 £ x

;

¤ õ ± ú É r ¸ ú 6 £ § (low-noise) : £ ¤$ í ` ¦ [1]. Õ ªo ¦, Al _x Ga ₁ _−x As 8 £ x \ " f Al ¸$ í (composition)\ É r DX

×

æd _ µ 1 ÏÒ q tÖ ¦ s Al ^x Ga 1 −x As/GaAs Ð s ` & h >

> ÷ & H X < [2], s H In y Ga ₁ _−y As G V , 8 £ x (channel layer) \ " f s " é ¶ l ^ (2-dimensional electron gas;

2DEG) 8 Z } É r ½ ¨5 Å q (confinement) õ s 1 l x ¸ M : ë

H s [3]. Õ ª õ , 400 GHz @ /% i _ è _ z ´ & ³ ¸ 0

p

x > % i . s ü < ° ú É r ½ ¨ ¸ s ü @\ ¸ # Q ì ø Í ¸^ \ ¦ s

6 xô Ç 8 £ x (multi-layer) ½ ¨ ¸\ " f_ : £ ¤$ í õ ¾ ¡ §| 9 É r & ³

@

/_ l & h , F g < Æ& h x 9 F g· l & h ì ø Í ¸^ è ] j r

l ì ø Ís ÷ & H × æ כ ¹ô Ç כ ¹| [ þ t s . ¾ ¡ §| 9 > h Ü ¼ Ð ô Ç

∗

E-mail: [email protected]

Ò q

tí ß | ¾ Ó_ 7 £ x @ /ü < $ § 4 ô Ç q 6 x Ü ¼ Ð" f ] j ) a è H q

õ , 6 x s ô Ç 6 x x 9 $ § 4 ô Ç q 6 x Ü ¼ Ð & ñ Ð_ ¸Ø ¦ É r J ? s

( ß ¼l (wafer scale)_ : £ ¤$ í ¨ î ~ ½ ÓZ O \ _ > r ) a . s

Qô Ç : £ ¤$ í ` ¦ é ß l 0 AK # Q z ´+ « >& h ~ ½ ÓZ O s 6 x ÷ &

%

3 . Õ ª × æ \ , ³ ð F g · ú ì rF gZ O (surface photovoltage spectroscopy; SPS) É r ª Ä ºÓ ü t > _ ì r$ 3 Ü ¼ Ð" f [4], q ] X

8 ú ¤ x 9 q õ : £ ¤$ í ` ¦ | 9 ÷ rë ß m , ü @Â Ò l © ` ¦

t · ú § ¸ $ : r÷ r ë ß m © : r \ " f ¸ 8 £ ¤& ñ Û ¼

&

7 à Ô! 3 \ " f : £ ¤$ í ` ¦ ¸ ú Ð# ï r H © & h s e # Q" f ì ø Í ¸

^

r « Ñ_ : £ ¤$ í ì r$ 3 Ü ¼ Ð Ä »6 xô Ç ~ ½ ÓZ O s .

: r ½ ¨\ " f H ì r \ x × þ r (molecular beam epi- taxy; MBE)Z O Ü ¼ Ð $ í © ô Ç Al _0.24 Ga _0.76 As/In _0.2 Ga _0.8 As /GaAs Ã » ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' ½ ¨ ¸_ : £ ¤$ í

`

¦ ³ ð F g · ú ì rF gZ O Ü ¼ Ð ½ ¨ % i . : £ ¤ y , z ´ : r \ " f 8

£

¤& ñ ô Ç (dV _ph /dE)/V _ph Û ¼& 7 à Ô! 3 Ü ¼ ÐÂ Ò' s \ -t

\

¦ ½ ¨ % i .

II. ÷ m Ç ] M ö

: r ½ ¨\ 6 xô Ç Al _0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs Ã

» ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' ½ ¨ ¸ Ð" f Fig. 1\

? /% 3 .

-238-

(2)

Fig. 1. Band diagram of Al _0.24 Ga _0.76 As/In _0.2 Ga _0.8 As/

GaAs p-HEMT

Fig. 1 \ " f © Â Ò\ " fÂ Ò' Y V Ð Ô ¦í HÓ ü t 0 l x ¸, ¿ ºa x 9

Ó ü t| 9 ` ¦ ? / , y y 2 × 10 ¹⁸ cm ⁻³ x 9 200 ˚ A_ GaAs Ö s8 £ x, 2 × 10 ¹⁷ cm ⁻³ x 9 200 ˚ A_ Al 0.24 Ga 0.76 As _

© # 4 8 £ x (barrier layer), Ô ¦í HÓ ü t` ¦ ' t · ú § É r 40 ˚ A _

Al 0.24 Ga 0.76 As_ s 8 £ x (space layer), 100 ˚ A_ In y

Ga 1 −y As_ G V , 8 £ x, 6 £ § Ü ¼ Ð GaAs x 9 10Å Òl _ AlAs/

GaAs í (supperlattices; SLs)_ ¢ - aØ æ8 £ x (buffer lay- er) s . ³ ð F g · ú 8 £ ¤& ñ É r chopped light geometryZ O

`

¦ 6 x % i . F G Ü ¼ Ð ´ o u- Å Ò$ 3 -í ß o8 £ x (Indium-tin- oxide; ITO)\ ¦ 7 £ x Ã Ìô Ç È Ò" î ô Ç ¸ Ä »o (transparent conducting glass; TCG)\ ¦ 6 x % i . 250 W_ ) í Û ¼ J $

½ + É Ð p Ï þ á Ôü < 0.75 m_ é ß Ò o o © u (monochroma- tor)_ ¸½ + ËÜ ¼ Ð 8 £ ¤& ñ F g " é ¶ Ü ¼ Ð 6 x % i . é ß Ò o o © u

\

¦ : x õ ô Ç ¸ F g " é ¶_ [ jl ü < ¸ Å Ò Ã º H y y 10 ⁻⁵ W/cm ² x 9 25 Hz Ð { 9 & ñ > % i . r « ÑÂ Ò' ¸Ø ¦ ) a

ñ H ½ © o ) a | Ã Ì 7 £ x; ¤ l \ ¦ 6 x # Ø ¦ % i .

III. + s ÇÊ Ý õ m Í À X Ø8 ý

Fig. 2 H p-HEMT r « Ñ\ @ /K : r ¸ 300 K\ " f 8 £ ¤

&

ñ ô Ç ³ ð F g · ú Û ¼& 7 à Ô! 3 ` ¦ · p כ s . Õ ªa Ë >\ " f

1.4 eV` ¦ l ï r Ü ¼ Ð, A _ \ -t @ /% i \ " f : r + þ A I

H In 0.2 Ga 0.8 As G V , 8 £ x_ F gf ¨ Ã º Ð K : r ñ Ð

"

f, 1.15 eVÂ Ò' # QL : (shoulder) x ß ¼ Ð" f × æ^ o ? ) a

ñ_ + þ AI Ð 7 £ x & ³ © ` ¦ Ð# Å Ò ¦ e . s \ ¦ ì r$ 3 l

0 AK Ä ºÛ ¼ ì r í (Gauss distribution) [5]\ ¦ s 6 x

#

x h Aô Ç õ \ " f In ^0.2 Ga 0.8 As G V , 8 £ x \ " f_ ª s

ñ_ 0 Au \ ¦ ¶ ú { 9 Õ ªa Ë >\ " f ¸ ú Ð# Å Ò ¦ e . s Q ô

Ç Û ¼& 7 à Ô! 3 % ! 3 F gf ¨ Ã ºü < ' aº ô Ç ñ_ + þ AI \ " f y

s \ @ /ô Ç & ñ Ð & ñ & h (peak) < Ê É r v 9 (dip)_ ñ + þ

AI Ð t · ú § ¦, Ô ¦ì r" î ô Ç â Ä º\ ½ ¨ H ~ ½ ÓZ O \

H # Q t e H X <, 0 A\ " f / å Lô Ç ~ ½ ÓZ O s ü @\ @ /

³

ð& h ~ ½ ÓZ O Ü ¼ Ð H ¿ º f _ §& h ` ¦ 6 x # ? /

H tangent intersection [6] x 9 { © o _ f ¨ Ã º Ð" f

Fig. 2. Phtovoltage spectrum as a function of photon energy at room temperature. Inset is present Gaussian’

fits

³

ð & ³ H 1 p ì r+ þ A ~ ½ ÓZ O 1 p x [7] s e . In ^0.2 Ga 0.8 As G

V , 8 £ x \ " f Ô ¦ì r" î ô Ç s ñ_ Å Ò ) a s Ä » H G V , 8 £ x _

Z } É r 0 l x ¸\ l ô Ç ` Ø Ôp ï r0 A s © \ " f G ¹ ¡ § (filling) & ³ © É r G V , 8 £ x \ " f_ f ¨ Ã º { 9 & ñ > ÷ &l M : ë

H s [8]. s Qô Ç ´ òõ H f ¨ Ã ºé ß (absorption edge)_

¦ \ -t s 1 l x (blue-shift) õ ¦ \ -t \ " f_ ñ ß ¼ l

y è > ÷ & ¦, G V , 8 £ x_ f ¨ Ã º\ Å Ò3 l q½ + Éë ß

>

o ) a . ¢ ¸ô Ç f ¨ Ã ºé ß _ ¦ \ -t s 1 l x É r G V , 8 £ x \

"

f 2DEG_ x 9 ¸ (electron sheet density)\ ¦ ½ ¨½ + É M : 6

x ) a [9]. 1.4 eV s © _ \ -t @ /% i \ " f : r + þ AI H GaAs, Al 0.24 Ga 0.76 As x 9 AlAs/GaAs í 8 £ x_ F gf ¨ Ã

º\ ' aº ) a ñs . ³ ð F g · ú \ @ /ô Ç ½ ¨ H s Q ô

Ç ~ ½ ÓZ O [ þ t` ¦ s 6 x # ´ ú § É r $ \ _ K 2 [/ å L ÷ &% 3 . · ú ¡

\

" f / å L % i 1 p w s , Ä ºÛ ¼ ì r í < ÊÃ º Ð" f ³ ð & ³ô Ç ¶ ú { 9 Õ

ªa Ë >\ " f y x ß ¼\ @ /ô Ç & ñ Ð & ñ S X t · ú §6 £ §` ¦ ^ ¦ Ã º e

. " f, : r ½ ¨\ " f 6 x| ¨ c p ì r ³ ð F g · ú ` ¦ s

K l 0 AK , 6 £ §_ # Q d [ þ t` ¦ ¸{ 9 % i . $ In y Ga 1 −y As G V , 8 £ x Ü ¼ ÐÂ Ò' ¸ H ³ ð F g · ú (V ph ) É r z

´] j_ ¸| s ë ß 7 á ¤| ¨ c M : f ¨ Ã º + þ AI (line-shape)\ ¦

Ø Ô> ) a . s H 6 £ § \ [ O " î ½ + É ¸| [ þ t \ _ K & ñ $ í & h Ü

¼ Ð è ß . [ jl φ 0 íl F g ¿ ºa L_ 8 £ x` ¦ :

x õ ½ + É M : f ¨ Ã º ) a F g _ [ jl H φ = φ 0 (1 − e ^−αL )

)

a . # l " f α H s Qô Ç % ò % i \ " f f ¨ Ã º > Ã ºs . s Q ô

Ç y n C\ _ K φ ⁰ (1 − e ^−αL )τ /~ω ü < 1 l x1 p xô Ç õ e ç H o # Q (excess carrier; ∆n) Ò q t$ í ) a . # l " f τ H H o # Q_ Ã

º" î r ç ß (lifetime)s ¦, ~ H Planck © Ã ºs 9, ω H y 1

l

x Ã º (angular frequency)s . ë ß { 9 1 αLs ) a ,

∆n = (φ 0 L/~ω)τ α ) a . G V , 8 £ x ? /\ l © s > r F

(3)

½ +

É M :, F gÒ q t$ í -& ñ / B N É r " f Ð ì ø Í@ /~ ½ Ó ¾ ÓÜ ¼ Ð s 1 l x ÷ & ¦,

³

ð F g · ú É r e∆n/C Ð" f V ph = (φ 0 eL/~ωC)τ α ) a

. # l " f C H & ñ 6 x| ¾ Ós . 0 A\ " f ¸ / å L % i 1 p w s

³

ð F g · ú É r F g _ [ jl ü < f ¨ Ã º\ & h Ü ¼ Ð _ > r

>

÷ & H X <, s \ ¦ # Q p ' \ ¦ í < Êô Ç d Ü ¼ Ð ³ ð & ³

6 £ § õ ° ú [7].

V _ph = φ(λ)α(λ)F (λ) (1)

³

ð & ³s 0 p x ¦, # l " f, F = F (L 0 , α, T, E f ; τ b , n b , p b ;

× E t , n _t σ _ph ⁿ , σ ^p _ph , e _n , e _p , S) Ð" f F H y y S X í ß U ´s (diffu- sion length; L ₀ ), f ¨ Ã º> Ã º, : r ¸(T ), ` Ø Ôp \ -t (E f ),

ü < & ñ / B N_ Ã º" î r ç ß (lifetime;τ _n , τ _p ) x 9 0 l x ¸(n b , p _b ), U

· É r ï r0 A \ -t x 9 0 l x ¸(n t ), t & ñ / B N Ü ¼ Ð" f_ F g s

: r o é ß (photoionzed cross section; σ _n , σ _p ), x 9 ~ ½ ÓØ ¦Ò ¦ (emission rate; e _n , e _p ) 1 p x_ 4 ¤¸ ú ô Ç < ÊÃ º Ð ½ ¨$ í ÷ &# Q e

. F G` ¦ t H F g _ È Òõ Ö ¦` ¦ Û ¼& 7 à Ô! 3 _ _ > r$ í

\

" f C ] j , F g _ [ jl ü < íl F g _ < ÊÃ º Ð ³ ð & ³

φ(λ) = φ ₀ (λ)α(λ) % ! 3 ç ß é ß y j þ t Ã º e . f ¨ Ã º> Ã

º_ Ã ºu & h p ì r õ Ä » < ÊÃ º p ì r+ þ A (dielectric function differential)_ ' a > ) a [10, 11]. " f, d (1)_ ' a >

\

¦ l : r Ü ¼ Ð # 1 p ì r ³ ð F g · ú Û ¼& 7 à Ô! 3 ` ¦ r

³ ð F g · ú Ü ¼ Ð ¾ º# Q" f Û ¦ s , 1

V _ph

∆V ph

∆E = a∆ε 1 + b∆ε 2 (2) s

[9,12]. # l " f aü < b H y y ¸ ì rF gZ O (modula- tion spectroscopy) \ " f Seraphin > Ã ºü < Ä » ¦, ∆ε 1

ü

< ∆ε ₂ H y y ¿ º > h_ H] X ô Ç \ -t ° ú כ\ " f 4 ¤¸ ú ô Ç Ä »

< ÊÃ º (ε = ε 1 + ε 2 )_ z ´Ã º (real)ü < ) Ã º (imaginary) כ

¹ ès . Å Ò# Q d (2)\ " f p ì r ' a > H { 9 ì ø Í& h Ü ¼ Ð Ä

»´ ò ¦, ∆ε 1 ü < ∆ε ₂ _ & ñ S X ô Ç < ÊÃ º& h + þ AI H Ó ü t o

&

h

+ þ A © \ ' aô Ç כ ë ß s e . ∆ε 1 ü < ∆ε ₂ _ ½ Ó[ þ t

É r Kramer-Kronig ' a > ü < ' a ) a . " f, Û ¼& 7 à Ô! 3 _

+ þ A © É r z ´Ã ºÂ Òì r (∆ε 1 )` ¦ ] jü @ô Ç ) Ã ºÂ Òì r` ¦ 6 £ § õ

°

ú s ³ ð & ³½ + É Ã º e [9,12].

ε ₂ = X

j

A _j {Im[ln(E − E j (mn) + iΓ _j )] }(1 − f e ^j ) (3)

#

l " f, A ^j H j P : + þ AI _ ; ¤ s ¦, E H F g \ -t , Γ j H & ³ © < Æ& h ¨ î ò ø Í (phenomenological broadening parameter) s 9, E j (mn) É r ? /Â Ò Â Ò{ (inter-subband) \

-t Ð" f 6 £ § õ ° ú .

E j (mn) = E ^C _m,j − E nj ^V (4)

Fig. 3. (dV ph /dE)/V ph spectrum as a function of photon energy at room temperature. Inset is present the line- shape’ fit in ranges from 1 to 1.4 eV.

d

(9)\ " f E m,j ^C ü < E _n,j ^V H y y j P : + þ AI ü < ' aº ) a m P

: ü < n P : & ñ / B N Â Ò{ ï r0 A\ " f_ \ -t s . Õ ª o

¦ ` Ø Ôp < ÊÃ º(f e ^j ) H 6 £ § Ü ¼ Ð ³ ð & ³ 0 p x .

f _e ^j = {exp[ηE − ηE j (mn) − E j (m)/kT ] + 1 } ⁻¹ (5)

E j (m) = (E f − E 1 ^C ) − (E m,j ^C − E 1 ^C ) (6)

#

l " f, E 1 ^C H ' Í P : Â Ò{ \ -t s . B j' η H 6 £ § Ü ¼ Ð Å Ò# Q .

η = m ^∗ _h

m ^∗ _e + m ^∗ _h (7)

#

l " f, m ^∗ e ü < m ^∗ _h H y y ü < 2 " é ¶ & ñ / B N_ Ä »´ ò| 9

|

¾ Ós . Fig. 3\ " f H Fig. 2_ ³ ð F g · ú Û ¼& 7 à Ô! 3

`

¦ (dV ph /dE)/V ph Ð · p כ s . ¶ ú { 9 Õ ªa Ë >\ " f ¸+ þ A ( ◦) H InGaAs G V , 8 £ x \ " f_ (dV ph /dE)/V ph s ¦ z ´ É r x

h Aô Ç õ s .

d

(4) ∼ (7) H (dV ph /dE)/V ph \ x h A` ¦ 0 Aô Ç Ã ºd s

. " f & ñ S X ô Ç y s _ ° ú כ` ¦ · ú Ðl 0 AK ,

Table 1. Transition energies in Al 0.24 Ga 0.76 As/In 0.2

Ga 0.8 As/GaAs p-HEMT at RT.

Transition Gauss’s fit.(eV) (dV

ph

/dE)/V

ph

fit.(eV)

11H 1.172 1.168

12H 1.220 1.211

21H 1.270 1.268

22H 1.316 1.313

32H 1.357 1.353

(4)

6 £

§_ õ & ñ ` ¦ ½ ÓÜ ¼ Ð ½ ¨ô Ç . $ , Ô ¦í HÓ ü t s ' ) a Al x Ga 1 −x As 8 £ x Ü ¼ ÐÂ Ò' s : r o ) a (ionized elec- tron) In y Ga ₁ _−y As G V , 8 £ x ? /\ 5 Å q& h Ü ¼ Ð / B N/ å L ÷ & ¦, s

[ þ t É r + þ A$ í ) a 2DEG \ 5 Å q& h Ü ¼ Ð % ò ¾ Ó` ¦ ï r .

" f Õ ªa Ë >_ mnH H m P : Â Ò{ ü < n P : & ñ / B N Â

Ò{ s s \ ¦ o . Fig. 1õ 2 ÐÂ Ò' ½ ¨ô Ç s

\

-t H Table 1 \ ? /% 3 . ¿ º õ H Ä » ô Ç ° ú כ` ¦

Ð# Å Ò% 3 .

IV. + s Ç Â ] Ø

· ú

ì rF gZ O Ü ¼ Ð ½ ¨ % i . p ì r+ þ A (dV ph /dE)/V ph Û ¼& 7 à

Ô! 3 Ü ¼ ÐÂ Ò' In 0.2 Ga _0.8 As G V , 8 £ x \ " f + þ A$ í ) a s \

-t \ ¦ ½ ¨ % i . s s \ -t H Ä ºÛ ¼ ì r í < ÊÃ º Ð

½

¨ô Ç ° ú כõ Ä » ô Ç õ \ ¦ Ð# Å Ò% 3 .

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 .

Y c

p w Ã U Ø ô

[1] R. Lee Ross, Stefan P. Svensson and Paolo Lugli, Pesudomorphic HEMT Technology and Applications (Academic press, 1994).

[2] F. Ail, and Gupta, HEMTs and HBTs: Device, Fab- rication and Circuits (Artech House, Boston, 1991).

[3] W. J. Schaff, P. J. Tasker, M. C. Foisy and L.

F. Bastman, Semiconductors and Semimetals (Aca- demic, New York, 1991). Vol. 33.

[4] A. Anedda, M. B. Casu and A. Serpi, J. Appl. Phys.

79, 6995 (1996).

[5] J. H. Kim, S. S. Choi, K. H. Kim, D. N. Kim and I.

H. Bae, J. Korean Phys. Soc. 39, 1023 (2001).

[6] J. Logowski, W. Walukiewicz, M. M. Slusarczuk and H. Gotas, J. Appl. Phys. 50, 5059 (1979).

[7] S. M. Eetemadi and R. Braustein, J. Appl. Phys.

58, 3856 (1985).

[8] D. S. Jinag, M. Goiran, J. Leotin, S. Askenazy, Y.

H. Zhang and K. Ploog, Phys. Status Solidi. B 179, 91 (1993).

[9] Y. Yin, H. Qiang, and F. H. Pollak, D. C. Streit and M. Wojtowicz, Appl. Phys. Lett. 61, 1579 (1992).

[10] S. Datta, S. Ghosh and B. M. Arora, Rev. Sci. In- strum. 72, 177 (2001).

[11] D. E. Aspnes, Modulation spectroscopy/electric field effects on the dielectric function of semiconductors in Handbook of Semiconductors (Northholand, Am- sterdam, 1980). Vol. 2.

[12] Y. Yin, H. Qiang, F. H. Pollak and T. F. Nobles,

Semicond. Sci. Technol. 8, 1599 (1993).

(5)

A Study on Al _0.24 Ga _0.76 As/In _0.2 Ga _0.8 As/GaAs Pseudomorphic High Electron Mobility Transistor Structure

by Using the Surface Photovoltage

Sang-Soo Choi and In-Ho Bae ^∗

Department of Physics, Daegu University, Gyoengsan 712-714

In-Soo Kim

Department of Visual Optics, Kyungwoon University, Gumi 730-852

Sung Bae Park

Department of Physics, Yeungnam University, Gyoengsan 712-749 (Received 30 May 2005, in final form 24 August 2005)

We studied the surface photovoltage characteristics of a Al

0.24

Ga

0.76

As/In

0.2

Ga

0.8

As/GaAs pse- domorphic high-electron-mobility transistor structure grown by using molecular beam epitaxy. The transitions in the quantum well are observed through the overlap signal in the surface photovoltage (SPV) spectrum. In order to analyze those transitions, we obtained the current positions from the normalized first derivative of the SPV fitted by a line shape function.

PACS numbers:

Keywords: Al

0.24

Ga

0.76

As/In

0.2

Ga

0.8

As/GaAs p-HEMT, SPV, Transition energy, (dV

ph

/dE)/V

ph

∗

E-mail: [email protected]

» ì Å ° Ë Ñ ¹ Å° q Ä Z Ø° Ë Ñ0 n É; c 8 ý X ¢ Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs  ¥y ¢] k ù w



» ì Å ° Ë Ñ ¹ Å°  q Ä Z Ø° Ë Ñ0 n É; c 8 ý X ¢ Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs  ¥y ¢] k ù w

 ¹ Å  T   Ò Þy ¢ ²   O U ­ ' [   º8 ý  ¤V R Ë

L

| ç ¡¬ £ · 9  - >  Ú ∗

% ò

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



»- > ¬ £

 â

î  r @ / < Æ § î ß  â F g < Æõ , ½ ¨p  730-852





) ç 9 

@

/½ ¨@ / < Æ § Ó ü t o  < Æõ ,  â í ß  712-714

(2005¸  5 Z 4 30{ 9  ~ Ã Î6 £ §, 2005¸  8 Z 4 24{ 9  þ j7 á x : r ~ Ã Î6 £ §)

ì

 r    \ x × þ r (MBE) Z O Ü ¼ Ð $ í  © ô  Ç Al

Ga

As/In

Ga

As/GaAs Ã » ¸+ þ A  ¦    s 1 l x  ¸ à

Ô ½ t Û ¼'  (p-HEMT) ½ ¨ ¸_  : £ ¤$ í `  ¦ ³ ð  F g  · ú  ì  rF gZ O  (SPS)Ü ¼ Ð   ½ ¨ % i  . ³ ð  F g  · ú    ñ



ÐÂ Ò'  In

Ga

þ

t É r s  : r° ú כõ   _  { 9 u  % i  .

PACS numbers: 71

Keywords: Al

Ga

As/In

Ga

As/GaAs Ã » ¸+ þ A  ¦    s 1 l x  ¸ à Ô ½ t Û ¼' , ³ ð  F g  · ú  ì  rF gZ O ,   s 

\

 -t 

I. " e Â ] Ø

Ã

» ¸+ þ A  ¦    s 1 l x  ¸ à Ô ½ t Û ¼'  (all pseudomorphic high electron mobility transistor; p-HEMT) ü < ° ú  É r    ¸



¸i ç  ) a (modulation-doped) ½ ¨ ¸_  Ó ü t o & h : £ ¤$ í x 9  è  6

£

x6 x Ü ¼ Ð" f ´ ú § É r   ½ ¨   '  ÷ &% 3  . : £ ¤ y , Al x Ga 1 −x As /In y Ga 1 −y As/GaAs ½ ¨ ¸  H Al x Ga 1 −x As/GaAs ½ ¨ ¸ü <

q

 § % i `  ¦ M : Z  } É r Å Ò Ã º\ " f  8¹ ¡ ¤  ¾ Ó ©  ) a   § 4 7 £ x

;



¤ õ  ± ú  É r ¸ ú 6 £ § (low-noise) : £ ¤$ í `  ¦    [1]. Õ ªo  ¦, Al x Ga 1 −x As 8 £ x \ " f Al  ¸$ í (composition)\    É r DX

×

 æd  _  µ 1 ÏÒ q tÖ  ¦ s  Al x Ga 1 −x As/GaAs  Ð   s `  & h >  

 >  ÷ &  H X < [2], s   H In y Ga 1 −y As G V , 8 £ x (channel layer) \ " f s  " é ¶    l ^  (2-dimensional electron gas;

2DEG)   8 Z  } É r     ½ ¨5 Å q (confinement) õ  s 1 l x  ¸ M : ë

 H s   [3]. Õ ª   õ , 400 GHz @ /% i _   è _  z ´ & ³ ¸  0

p

x >  % i  . s ü < ° ú  É r ½ ¨ ¸ s ü @\  ¸ #  Q ì ø Í ¸^ \  ¦ s

6 xô  Ç 8 £ x (multi-layer) ½ ¨ ¸\ " f_  : £ ¤$ í õ  ¾ ¡ §| 9  É r  & ³

@

/_    l & h , F g < Æ& h x 9 F g·  l & h   ì ø Í ¸^   è  ] j   r

 l ì ø Ís  ÷ &  H ×  æ כ ¹ô  Ç כ ¹| [ þ t s  . ¾ ¡ §| 9  > h  Ü ¼ Ð   ô  Ç

E-mail: [email protected]

Ò q

tí ß | ¾ Ó_  7 £ x @ /ü < $ § 4 ô  Ç q 6 x Ü ¼ Ð" f ] j   ) a  è   H q 

õ , 6 x s ô  Ç  6 x x 9 $ § 4 ô  Ç q 6 x Ü ¼ Ð & ñ  Ð_   ¸Ø  ¦ É r J ? s

(  ß ¼l  (wafer scale)_  : £ ¤$ í ¨ î  ~ ½ ÓZ O \  _  > r ) a . s 



Qô  Ç : £ ¤$ í `  ¦   é ß  l  0 AK  #  Q z ´+ « >& h ~ ½ ÓZ O s   6 x ÷ &

%

3  . Õ ª ×  æ \ , ³ ð  F g  · ú  ì  rF gZ O  (surface photovoltage spectroscopy; SPS) É r  ª  Ä ºÓ ü t > _  ì  r$ 3 Ü ¼ Ð" f [4], q  ] X

8 ú ¤ x 9 q  õ : £ ¤$ í `  ¦ | 9  ÷  rë ß   m  , ü @Â Ò  l  © `  ¦



  t  · ú §  ¸ $  : r÷  r ë ß   m    ©  : r \ " f ¸ 8 £ ¤& ñ Û ¼

&

7 à Ô! 3 \ " f : £ ¤$ í `  ¦ ¸ ú   Ð# ï  r   H  © & h s  e  # Q" f ì ø Í ¸

^

 r « Ñ_  : £ ¤$ í ì  r$ 3 Ü ¼ Ð Ä »6 xô  Ç ~ ½ ÓZ O s  .



: r   ½ ¨\ " f  H ì  r    \ x × þ r  (molecular beam epi- taxy; MBE)Z O Ü ¼ Ð $ í  © ô  Ç Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As /GaAs Ã » ¸+ þ A  ¦    s 1 l x  ¸ à Ô ½ t Û ¼'  ½ ¨ ¸_  : £ ¤$ í

`

» ì Å ° Ë Ñ ¹ Å° q Ä Z Ø° Ë Ñ0 n É; c 8 ý X ¢ Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs ¥y ¢] k ù w

» ì Å ° Ë Ñ ¹ Å° q Ä Z Ø° Ë Ñ0 n É; c 8 ý X ¢ Al 0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs ¥y ¢] k ù w

¹ Å T Ò Þy ¢ ² O U ' [ º8 ý ¤V R Ë

| ç ¡¬ £ · 9 - > Ú ^∗

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

â

î r @ / < Æ § î ß â F g < Æõ , ½ ¨p 730-852

) ç 9

/½ ¨@ / < Æ § Ó ü t o < Æõ , â í ß 712-714

(2005¸ 5 Z 4 30{ 9 ~ Ã Î6 £ §, 2005¸ 8 Z 4 24{ 9 þ j7 á x : r ~ Ã Î6 £ §)

r \ x × þ r (MBE) Z O Ü ¼ Ð $ í © ô Ç Al

As/GaAs Ã » ¸+ þ A ¦ s 1 l x ¸ à

Ô ½ t Û ¼' (p-HEMT) ½ ¨ ¸_ : £ ¤$ í ` ¦ ³ ð F g · ú ì rF gZ O (SPS)Ü ¼ Ð ½ ¨ % i . ³ ð F g · ú ñ

ÐÂ Ò' In

t É r s : r° ú כõ _ { 9 u % i .

As/GaAs Ã » ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' , ³ ð F g · ú ì rF gZ O , s

-t

» ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' (all pseudomorphic high electron mobility transistor; p-HEMT) ü < ° ú É r ¸

¸i ç ) a (modulation-doped) ½ ¨ ¸_ Ó ü t o & h : £ ¤$ í x 9 è 6

x6 x Ü ¼ Ð" f ´ ú § É r ½ ¨ ' ÷ &% 3 . : £ ¤ y , Al ^x Ga 1 −x As /In y Ga 1 −y As/GaAs ½ ¨ ¸ H Al x Ga 1 −x As/GaAs ½ ¨ ¸ü <

§ % i ` ¦ M : Z } É r Å Ò Ã º\ " f 8¹ ¡ ¤ ¾ Ó © ) a § 4 7 £ x

¤ õ ± ú É r ¸ ú 6 £ § (low-noise) : £ ¤$ í ` ¦ [1]. Õ ªo ¦, Al _x Ga ₁ _−x As 8 £ x \ " f Al ¸$ í (composition)\ É r DX

æd _ µ 1 ÏÒ q tÖ ¦ s Al ^x Ga 1 −x As/GaAs Ð s ` & h >

> ÷ & H X < [2], s H In y Ga ₁ _−y As G V , 8 £ x (channel layer) \ " f s " é ¶ l ^ (2-dimensional electron gas;

2DEG) 8 Z } É r ½ ¨5 Å q (confinement) õ s 1 l x ¸ M : ë

H s [3]. Õ ª õ , 400 GHz @ /% i _ è _ z ´ & ³ ¸ 0

x > % i . s ü < ° ú É r ½ ¨ ¸ s ü @\ ¸ # Q ì ø Í ¸^ \ ¦ s

6 xô Ç 8 £ x (multi-layer) ½ ¨ ¸\ " f_ : £ ¤$ í õ ¾ ¡ §| 9 É r & ³

/_ l & h , F g < Æ& h x 9 F g· l & h ì ø Í ¸^ è ] j r

l ì ø Ís ÷ & H × æ כ ¹ô Ç כ ¹| [ þ t s . ¾ ¡ §| 9 > h Ü ¼ Ð ô Ç

tí ß | ¾ Ó_ 7 £ x @ /ü < $ § 4 ô Ç q 6 x Ü ¼ Ð" f ] j ) a è H q

õ , 6 x s ô Ç 6 x x 9 $ § 4 ô Ç q 6 x Ü ¼ Ð & ñ Ð_ ¸Ø ¦ É r J ? s

( ß ¼l (wafer scale)_ : £ ¤$ í ¨ î ~ ½ ÓZ O \ _ > r ) a . s

Qô Ç : £ ¤$ í ` ¦ é ß l 0 AK # Q z ´+ « >& h ~ ½ ÓZ O s 6 x ÷ &

3 . Õ ª × æ \ , ³ ð F g · ú ì rF gZ O (surface photovoltage spectroscopy; SPS) É r ª Ä ºÓ ü t > _ ì r$ 3 Ü ¼ Ð" f [4], q ] X

8 ú ¤ x 9 q õ : £ ¤$ í ` ¦ | 9 ÷ rë ß m , ü @Â Ò l © ` ¦

t · ú § ¸ $ : r÷ r ë ß m © : r \ " f ¸ 8 £ ¤& ñ Û ¼

7 à Ô! 3 \ " f : £ ¤$ í ` ¦ ¸ ú Ð# ï r H © & h s e # Q" f ì ø Í ¸

r « Ñ_ : £ ¤$ í ì r$ 3 Ü ¼ Ð Ä »6 xô Ç ~ ½ ÓZ O s .

: r ½ ¨\ " f H ì r \ x × þ r (molecular beam epi- taxy; MBE)Z O Ü ¼ Ð $ í © ô Ç Al _0.24 Ga _0.76 As/In _0.2 Ga _0.8 As /GaAs Ã » ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' ½ ¨ ¸_ : £ ¤$ í

¦ ³ ð F g · ú ì rF gZ O Ü ¼ Ð ½ ¨ % i . : £ ¤ y , z ´ : r \ " f 8

¤& ñ ô Ç (dV _ph /dE)/V _ph Û ¼& 7 à Ô! 3 Ü ¼ ÐÂ Ò' s \ -t

¦ ½ ¨ % i .

: r ½ ¨\ 6 xô Ç Al _0.24 Ga 0.76 As/In 0.2 Ga 0.8 As/GaAs Ã

» ¸+ þ A ¦ s 1 l x ¸ à Ô ½ t Û ¼' ½ ¨ ¸ Ð" f Fig. 1\

? /% 3 .

Fig. 1. Band diagram of Al _0.24 Ga _0.76 As/In _0.2 Ga _0.8 As/

Fig. 1 \ " f © Â Ò\ " fÂ Ò' Y V Ð Ô ¦í HÓ ü t 0 l x ¸, ¿ ºa x 9

Ó ü t| 9 ` ¦ ? / , y y 2 × 10 ¹⁸ cm ⁻³ x 9 200 ˚ A_ GaAs Ö s8 £ x, 2 × 10 ¹⁷ cm ⁻³ x 9 200 ˚ A_ Al 0.24 Ga 0.76 As _

© # 4 8 £ x (barrier layer), Ô ¦í HÓ ü t` ¦ ' t · ú § É r 40 ˚ A _

Al 0.24 Ga 0.76 As_ s 8 £ x (space layer), 100 ˚ A_ In y

Ga 1 −y As_ G V , 8 £ x, 6 £ § Ü ¼ Ð GaAs x 9 10Å Òl _ AlAs/

GaAs í (supperlattices; SLs)_ ¢ - aØ æ8 £ x (buffer lay- er) s . ³ ð F g · ú 8 £ ¤& ñ É r chopped light geometryZ O

¦ 6 x % i . F G Ü ¼ Ð ´ o u- Å Ò$ 3 -í ß o8 £ x (Indium-tin- oxide; ITO)\ ¦ 7 £ x Ã Ìô Ç È Ò" î ô Ç ¸ Ä »o (transparent conducting glass; TCG)\ ¦ 6 x % i . 250 W_ ) í Û ¼ J $

½ + É Ð p Ï þ á Ôü < 0.75 m_ é ß Ò o o © u (monochroma- tor)_ ¸½ + ËÜ ¼ Ð 8 £ ¤& ñ F g " é ¶ Ü ¼ Ð 6 x % i . é ß Ò o o © u

¦ : x õ ô Ç ¸ F g " é ¶_ [ jl ü < ¸ Å Ò Ã º H y y 10 ⁻⁵ W/cm ² x 9 25 Hz Ð { 9 & ñ > % i . r « ÑÂ Ò' ¸Ø ¦ ) a

ñ H ½ © o ) a | Ã Ì 7 £ x; ¤ l \ ¦ 6 x # Ø ¦ % i .

Fig. 2 H p-HEMT r « Ñ\ @ /K : r ¸ 300 K\ " f 8 £ ¤

ñ ô Ç ³ ð F g · ú Û ¼& 7 à Ô! 3 ` ¦ · p כ s . Õ ªa Ë >\ " f

1.4 eV` ¦ l ï r Ü ¼ Ð, A _ \ -t @ /% i \ " f : r + þ A I

H In 0.2 Ga 0.8 As G V , 8 £ x_ F gf ¨ Ã º Ð K : r ñ Ð

f, 1.15 eVÂ Ò' # QL : (shoulder) x ß ¼ Ð" f × æ^ o ? ) a

ñ_ + þ AI Ð 7 £ x & ³ © ` ¦ Ð# Å Ò ¦ e . s \ ¦ ì r$ 3 l

0 AK Ä ºÛ ¼ ì r í (Gauss distribution) [5]\ ¦ s 6 x

x h Aô Ç õ \ " f In ^0.2 Ga 0.8 As G V , 8 £ x \ " f_ ª s

ñ_ 0 Au \ ¦ ¶ ú { 9 Õ ªa Ë >\ " f ¸ ú Ð# Å Ò ¦ e . s Q ô

Ç Û ¼& 7 à Ô! 3 % ! 3 F gf ¨ Ã ºü < ' aº ô Ç ñ_ + þ AI \ " f y

s \ @ /ô Ç & ñ Ð & ñ & h (peak) < Ê É r v 9 (dip)_ ñ + þ

AI Ð t · ú § ¦, Ô ¦ì r" î ô Ç â Ä º\ ½ ¨ H ~ ½ ÓZ O \

H # Q t e H X <, 0 A\ " f / å Lô Ç ~ ½ ÓZ O s ü @\ @ /

ð& h ~ ½ ÓZ O Ü ¼ Ð H ¿ º f _ §& h ` ¦ 6 x # ? /

H tangent intersection [6] x 9 { © o _ f ¨ Ã º Ð" f

ð & ³ H 1 p ì r+ þ A ~ ½ ÓZ O 1 p x [7] s e . In ^0.2 Ga 0.8 As G

V , 8 £ x \ " f Ô ¦ì r" î ô Ç s ñ_ Å Ò ) a s Ä » H G V , 8 £ x _

Z } É r 0 l x ¸\ l ô Ç ` Ø Ôp ï r0 A s © \ " f G ¹ ¡ § (filling) & ³ © É r G V , 8 £ x \ " f_ f ¨ Ã º { 9 & ñ > ÷ &l M : ë

H s [8]. s Qô Ç ´ òõ H f ¨ Ã ºé ß (absorption edge)_

¦ \ -t s 1 l x (blue-shift) õ ¦ \ -t \ " f_ ñ ß ¼ l

y è > ÷ & ¦, G V , 8 £ x_ f ¨ Ã º\ Å Ò3 l q½ + Éë ß

o ) a . ¢ ¸ô Ç f ¨ Ã ºé ß _ ¦ \ -t s 1 l x É r G V , 8 £ x \

f 2DEG_ x 9 ¸ (electron sheet density)\ ¦ ½ ¨½ + É M : 6