The excitonic properties and temperature behaviour of the photoluminescence from GaAs-GaAlAs multiple quantum well structures

~

Solid State Co~nunications, Vol.6I,No.11, pp.707-71|, Printed in Great Britain.

THE EXCITONIC

PROPERTIES

AND TEMPERATURE

SC~.NCE FROM G a A s - G a A I A s Xu Zhongying,

MULTIPLE

Xu Jizong,

Xu J u n y i n g Institute

BE~L%VIOUR O F THE P H O T O L U M I R ~ QUANTUM

Ge Weikun,

WELL STRUCTURES

Zheng

Baozhen

and Li Y u z h a n g

of S e m i c o n d u c t o r

Academia

0038-1098/87 $3.00 + .00 Pergamon Journals Ltd.

198Z

Sinica,

Physics,

Beijing,

China

(Received 3 December 1986 by W. Y. Kuan) The t e m p e r a t u r e recombination

characteristics

in m u l t i p l e

investigated

in detail

the m a t e r i a l

quality.

There

have b e e n

on the o p t i c a l quantum

well

vestigation

Also

well

structures

to be a g o o d

reported

radiative have b e e n

assessment

is the c o m p e t i t i o n with

different

pheno-

widths

a number

Therefore

of reports

haviour

of p _ ~ s - G a A i A s

(QWs).

low t e m p e r a t u r e

the d e s c r i b e d

can be used

The in-

material

photolu-

observed, for

quality.

temperature

be-

to c h a r a c t e r i z e

the

In addition,

the first

(PL) and p h o t o l u m i n e s c e n c e

tition

excitation

(PLE)

combinations

from wells

widths.

competition

from high quality

attributed tion~

s h o w that

for r o o m

there are s i g n i f i c a n t the r e p o r t e d

but

paper

vestigation

recombina-

temperature

from

quantum

structures show

but

thermally

dissociate

the free c a r r i e r quantized

temperature

of the exciton

sample

to sample;

the i n t r i n s i c be observed

on a s e m i -

GaAs

substrate, with

while with

with

with

Sample

15 periods

2 was of 125

and 220 ~ wide barriers, 3 was

15 periods

capped

between

a GaAs-GaAIAs

of Lz=d9

~ and

a I000 ~ GaAIAs

51QWs

%=150

~,

cladding

layer.

predominant.

varies

sample

a 0.i )/m G a A I A s

on the top.

MQWs

of

a 0.2 )/m

and a well

and finally

layer

w i d e wells

in

The c o n v e n t i o n a l in the experiment.

from

recombination

even at room

wells,

cladding

for high quality

exciton

(i00)

barrier

epi-

1 consisted

sequence:

deposited

undoped

a GaAs-AIAs

that the d i s s o c i a t i o n

found

Sample

beam

GaAs

and c o n s e q u e n t l y

It has b e e n

layer

molecular

multiple

exciton may

becomes

is t e m p e r a t u r e

L =190 ~, ~ o l l o w e d by 5 periods of alz t e r n a t i v ~ 70 ~ GaAIAs b a r r i e r s and 141

is e x c i t o n i c

recombination

subbands

hole redifferent

of the

properties

(MQWs).

the i n t r i n s i c

with

in this work were

layer

a 70 ~ O a A l \ s

in-

that at low t e m p e r a -

the PL from QWs

buffer

insulating

mechanism.

behaviour

used

system.

GaAs

from GaAs-GaAIAs

ture,

(~E)

interpreta-

luminescence

nature,

taxy

controversial

of the e x c i t o n i c

~ell

The samples

various

a detailed

electron-heavy

g r o w n by a h o m e - m a d e

in

the f o l l o w i n g

we report

we have

the c o m p e -

dependent.

PL

have y i e l e d

and the t e m p e r a t u r e

T h e results

This

results

on the r e c o m b i n a t i o n

In this

are m a i n l y

differences

PL spectra

laboratories~,~hese

tions

QWs

to the e x c i t o n i c

however,

valuable,

the lumine-

between

time,

minescence

scence

for

sample.

properties

structures of

quantum

and s h o w n

f r o m q u a n t u m wells

mena of emissions in the same

of the e x c i t o n i c

ted by an argon

QWs

5145 ~. The

can

a Spex

temperature. 707

ion

PL t e c h n i q u e The s a m p l e

was

was

exci-

laser o p e r a t i n g

luminescence

was

used

at

analyzed

1403 d o u b l e m o n o c h r o m a t o r

by

and de-

708

Vol. 61, No. I I

PHOTOLUMINESCENCE FROM GaAs-GaAIAs MULTIPLE QUANTUM WELL STRUCTURES

tected

by

tiplier

a cooled

tube

RCA 31034A

with

a flat

photomul-

spectral

resA

ponse

in the s p e c t r a l

Figure ture two

i shows

a typical

(I11<) PL s p e c t r u m peaks

noted the

range

at

Xs

1.536

Elh and

expected

1.526

trinsic

excitonic

the QWs

with

L =141

~ and

each

On

peak

these

respective trinsic

is a w e a k

n=l

peaks

ted

as Ell that

and

peak

a very

good

Figure dence

sample.

width

we

as

1.9 m e v quality

observed

the

for of

the

in-

1.4.2

>-

1-46

for

the

Fig.2.

Photoluminescence

E{h , i n d i c a t i n g

sample

the m a t e r i a l .

from

was

increased

(i) a d e c r e a s e

of the

high

energy

i.e.

the a p p e a r a n c e

E1h

slope

(iii)

thermal

is

narrower wider

wells

well

IIK

Elh

as the

10OK

surpassed

low t e m p e r a t u r e ( I l K )

GaAs/GaAIAs

of a h i g h MQW

quality

(sample

I).

samples

the s u b b a n d s

feature

and

elec-

from

the

from

the

that

this

dependent.

is s t r o n g e r

than

of

S{h is

At

E{h'

is i n c r e a s e d

the

enhanced.

m' has a l r e a d y -lh o f Elh ; w i t h a f u r t h e r of

temperature

as s h o w n

with

between

temperature

that

has

in the

that

intensity

of

in

It is f o u n d

temperature

the

behaviour

spectrum

is

intensity

increase again,

(Elh)

emission

relative

of

All

explained

recombinations

(ZLh).

competition

and

(E2h,Z~h)._

the c o m p e t i t i o n hole

the

dimensions.

interesting

tron-heavy

of

of h i g h e r

can be

population

two-nonconfined

spectra

\t

emissions

observations

A very

Z

the a p p e a r a n c e

related

by

an i n c r e a s e

tails

(ii)

11K

152 1.54. ENERGY (eV)

lines,

energy

of E l i ( E { 1 ) to E l h ( E { h )

ratio

these

&

the s p e c t r a l of high

in the s p e c t r a ;

subband

E]h, i

of

intensity

of

\ typical

from

tempera-

tures.

the

PL

spectra

1 at d i f f e r e n t

depen-

the s a m e

Z LLI

Fig.l.

1.54

ENERGY (eV)

noti-

M0W

1.50

1.50

at half maximum

temperature

that:

the

(deno-

temperature

~As/~AI As

I-.-

18oK

that

lines;

.4

F\4L-

of

to

hole

1.7 m e v

the PL s p e c t r a As

related

Ell-'). It is w o r t h

2 shows

of

/

The

recombinations

the full

and

peak.

suggests

are

(FWH]"4) is as n a r r o w Elh

% 2 oK

from

side

electron-light

excitonic

cing

energy

calculation

two w e a k

Y

Z

the h i g h

there

theoretical

Z

in-

L =190 ~ r e s -

Z

pectively.

to

hole

E;h

h

de-

attributed

recombinations

300K

I. The ev,

electron-heavy

, ~

.4

low t e m p e r a -

of s a m p l e

ev and

Elh,~' are

n=l

of interest.

in Fig.

been

reason

for

we b e l i e v e

this

2. The

observed

different

clear;

Elh d o m i n a t e s

structures.

phenomenon that

similar

in other The

is not yet

it has

to do w i t h

PHOTOLUMINESCENCE

Vol. 61, No. 11 trapping

and diffusing

toexcited

carriers

different

thermal

FROM GaAs-GaA]As MULTIPLE QUANTUM WELL STRUCTURES

processes

of pho-

behaviour

of

as

position

temperatures

temperature.

For

the s a k e

of compa-

ference

the

experimental

dependence

also

shown.

peak

of QW material

shifted

(Eg),

tion,

of bulk

of

band

which

for

tempera-

that

the

reflects To

tely

deep well, shift

the

amount

of

3 the

ferent

data

samples

follows Blh difference from

are

temperature;

plotted.

Eg v e r y between very

For

closely,

two

dif-

sample

the

i

energy

Elh

low

for

from

a n d Eg k e e p s c o n s temperature up to room

sample

peak obviously

does

low

E . For the sake g c u r v e was r e d r a w n t o

of

3,

however,

the

not

closely

fol-

clarity

coincide

the

are not due

"]

has b e e n

-

theoretical

both

transition

processes,

results

good

300

the

temperatures samples.

for

Elh p e a k

in b e t w e e n .

clearly

to c h a r a c t e r i z e

used

quality.

excitonic

two

For

Usually

its

room

different

related trum,

the

luminescence

implying

latively

high

that

material 1 has

excitons. low tem-

3 is as strong

appears

large

as

impurity

in the s p e c -

the s a m p l e

impurity

a very conse-

radiative

by

F[~%i o f

relatively

tempera-

before,

temperature

PL f r o m s a m p l e

and

4.

can be regar-

sample

the

ex-

the m a -

room

of good

is d o m i n a t e d hand

Our

described

the

as d e s c r i b e d

t

in Figure

luminescence

example,

quality

the

demonstrate

behaviour

perature

vs.

exponent

temperature

the o t h e r

9 mev

~en

can be

recombination On

t=2.

an for

is a s s o c i a t e d

as s h o w n

quality.

I

of

(2)

for

while

properties,

quently

energy

analysis

Pin t '

t=l,

recombination

lie s o m e w h e r e

terial

%IaaAsl~

Photon

the

intensity

of recombination:

d e d as an i n d i c a t i o n

Fig.3.

by

as

recombination

carrier

should

ture

T(K)

confirmed

P

The

200

identi-

thermal

of PL integrated

can be written

above

100

iOO

The above

the P L i n t e g r a t e d

these

0

clearly

A simple

perimental

I

of

involved.

to t h e

sho=vs that

with

1.55

1.45

are

intensity.

free

oXo

processes

tem-

range

dependence

the mechanism

I

1.50

at h i g h

to

is the e x c i t a t i o n i n t e n s i t y a n d in C a c o n s t a n t . T h e e x p o n e n t t d e p e n d s on

g Blh

L

exci~o-

l o w temperature

excitation

luminescence

=I"+"~--~i.

is in g o o d

PL emission

temperature

they

identification

where

At

dif-

the i n t r i n s i c

at

effect.

excitonic I

the

PL(I)=C

E

with

that

in t h e s p e c t r a

PL(I)

cur-

changed. energy

which

recombination

both

broadening

)

is

two

exciton binding energy 6 It is t h e n r e a -

from

In t h e

K to 2OOK,

fied

obtained

carrier

the

et al.

varies

Neverthless

(!

the

the

the

8 mev,

to s u g g e s t

perature.

the spec-

2OOK

recombination

free

infini-

Z

Fig.

nic

approxima-

is g i v e n b y ~ 2 , ~ ,2 E=="~-~ ( L-- ) .

with

by

It is o b s e r v e d

temperature

5y Greene

process

an intrinsic

the f i r s t

given

sonable

band

3.

between

above

is a b o u t

agreement

is

PL

from GaAs

a one-dimensional

tral

gap

is s i g n i f i c a n t l y

energy

o f QWs.

i.e.

data GaAs

It c a n b e s e e n

to h i g h e r

property

Elh

varies

Elh peak

ture

rant

in Fig.

the

rison,

In

line

as i n d i c a t e d

the d i f f e r e n c e

3 shows

Figure

gap

that ves

luminescence.

vs.

low temperature,

dashed

in t h e MQtqs a n d w i t h quenching

at

709

has

a re-

concentration.

710

PHOTOLUMINESCENCE

FROM

GaAs-GaAIAs

d

MULTIPLE

QUANTUM

quenching from

three

/ +

1.Z,2

regions

z

slowly;

in }he high

I l

l

III

I

100

Excitation

sity

dependence

of inte-

photoluminescence

inten-

temperatures.

The exponent t in t ?L(I)=C Pin is also

A simplified

perature

dependence

Consistently,

its

room t e m p e r a t u r e

is d o m i n a t e d

As shown

BIe-E/KT

dependence

is c o n s i d e r a b l y

QWs

is of less

due

to the excitonic

FWHM

The

at higher

experimental

of carriers.

increases

much more

sociation fairly

Finally

dat~

the

exciton

and by fitting

it is o b t a i n e d 7.5

6.5meV

(sample

respectively.

that

i),

these

meV

values

with

the exciton binding

from

figure

recom-

the

that

S=

(sample 2 ] and It is

are c o n s i s t e n t energy

derived

3. the e x p e r i m e n t a l

in this

r /

paper

show

that

bulk /

/

-/

/

results the des-

~y

from

b_+_+-+-/

/ J-."<_/.>-/.t"f / sompL~ y// .f"

of the l)the

at low tem-

due to the therma=, However,

quickly

of excitons.

the FWHM

in p a r t i c u l a r

the

thermal

dis-

These

results

are

with

the above

expe~

results. we discuss

(3)

a bit more q u i c k l y

2, indicating

in a g r e e m e n t

rimental

luminescence as

(sample 3),

dependence~

very s l o w l y

lization

tem-

that of

(as for sample

temperature

for sample

from

properties

and i n c r e a s e d

is as-

of the

8.5meV

carriers

~VHM of spectra

Typically

recom-

width of QWs

temperature

is i n c r e a s e d

perature

the

represents

5, the t e m p e r a t u r e

different

material.

emission.

by free

of the spectral

bulk

to

dissociation

model

of

process

excitons. in Eimure

due

quenching

can be e x p r e s s e d

dissociation

reported

than

reduced

the exciton

In conclusion,

indicated.

rather

luminescence

process.

noticed

(sample 3 ) at different

equation

region,

quickly,the

In the i n t e r m e d i a t e

with

where

EXCITATION INTENSITY( W/crn2 )

grated

very

I i i i i,,l

10

bination

or varies

Io~A/(l+Ble-E/;
le I

Fig.4.

low in-

non-radiative

sociated

intensity

are

In the

temperature

activated

the

experimental

is q u e n c h e d

mechanism.

region,

11

No.

luminescence

is e x p o n e n t i a l l y

thermally bination

the

constant

luminescence

61,

6. There

for each curve.

region,

keeps

intensity

The

in Figure

tensity

the

Vol.

of the Elh l u m i n e s c e n c e

samples.

are shown

temperature ,

STRUCTURES

process

different

results

20K

WELL

0

Fig.5.

50

The full w i d t h (FW~I)

the t e m p e r a t u r e

100

150

200 T (K)

25(

at half m a x i m u m

of Elh r e c o m b i n a t i o n

temperature.

vs.

Vol. 61, No. !1

100 50 |

20

I

10

!

low t e m p e r a t u r e

( K)

I

+ >-

temperature

keep

i.e.slow

tion f r o m carrier from the

luminescence

terial,and •- . o - SAMPLE

1

-+-

3

...-o-

2

The

strong

I ~1

I

f )I' 0

I

'

' 1201

relationship peak

energy

Fig.6.

The

temperature

the

luminescence

exciton

excitation

been

data with

The

E have

deduced by fitting

periment the

energy

luminescen-

ce is a f o u n d a m e n t a l

feature

which

from

the two d i m e n s i o n a l

ty of the Q ~

and d i s t i n g u a s h e s

from

material.

the b u l k

detector,and

devices,

especially

lication

at room

cribed

the ex-

Eo.(3)

(see

tion

properties

quality.

of the Q W

can be used as a good

for the a s s e s s m e n t

should

In brief, have

the Qws

devices,

optical their

e.g.

bistability

practical

app-

fact

the e x c i t o n i c

rect

judgement

licable

property.

Thus

for s e l e c t i n g

QW materials

depends

a di-

device

is g i v e n

in

app-

in this

paper.

text).

excitonic

ori-

proper-

The p e r f o r m a n c e

temperature,

\cknowledgement-We

minescence

de-

intensity.

of

intensity.

binding

bulk ma-

exeiton

laser,

dependence

between

and the

luminescence

of the QWs o p t o e l e c t r o n i c

lO00/T (l/K)

to free

can be i d e n t i f i e d

intrinsic

ginates

I

recombination

the different

of the

linear

The t r a n s f o r m a -

gap of the c o r r e s p o n d i n g

pendence

of s p e c -

of the i n t e g r a t e d

recombination

the r e l a t i v e

band

luminescence

temperature,

intensity.

exciton

range o f

variation

dependence

luminescence

f

excitonic

line w i d t h with

excitation

Z u.l Z J

and in a wide

properties, tral

//

0

711

PHOTOLUMINESCENCE FROM GaAs-GaA|As MULTIPLE QUANTUM WELL STRUCTURES

lu-

indica-

of the m a t e r i a l

a high quality

narrow spectral

Professor and

Kun

and Chen

Sun

Zunggui

samples.

This

at

National

Science

to

for his s u p e r v i s i o n

to I
Jiben

HQWs

lines

are very g r a t e f u l

Huang

work was

Dianzhao,

hiang

for p r o v i d i n g supported

by

the

Foundation.

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L~tt.

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H.I.Ralph Rev.

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