TELKOM
NIKA Indonesia
n
Journal of
Electrical En
gineering
Vol. 16, No. 3, Dece
mbe
r
2
015, pp. 502
~ 508
DOI: 10.115
9
1
/telkomni
ka.
v
16i3.937
8
502
Re
cei
v
ed Au
gust 23, 20
15
; Revi
sed
No
vem
ber 8, 20
15; Accepted
No
vem
ber 2
2
,
2015
Effect of Thermal
Annealing T
e
mperatures on MSM
Photo Detector Based on Ge-like Micr
o Flowers in the
Dark Mode
M.J. Ja
w
a
d, Haider Y. Ha
m
m
od, Am
er B. Dhey
ab*
Ministr
y
of scie
n
ce an
d techn
o
lo
g
y
/
Director
a
te of
material R
e
searc
h
/cente
r
of laser resea
r
ch
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: amer.alj
obur
i
@
yah
oo.com
)
A
b
st
r
a
ct
In this researc
h
, a current de
nsity of J =
7.5
mA
/cm2 w
a
s app
lie
d over a
c
onstant dur
ati
on of 2 h
to grow
Ge-lik
e
microfl
o
w
e
rs on S
i
. T
o
fa
br
icate
a
p
hoto
d
e
tector, Pd w
a
s de
posite
d
by
RF
-sputterin
g
as
m
e
tal contact with Ge
.
T
he sampl
e
s w
e
re subj
ected to ra
pid t
her
ma
l an
nea
lin
g (RT
A
) in a
m
bi
ent N2
at
100
,
200°
and
300°C for 1
0
mi
n
.
By screen
ing the s
a
mpl
e
s from
el
ectric
al no
is
e, the electri
c
al
character
i
stics
throug
h curr
en
t-voltage
meas
ure
m
e
n
ts w
e
re
carrie
d
o
u
t at
roo
m
te
mpera
t
ure b
e
fore
an
d
after an
nea
lin
g
.
T
he meas
ure
m
e
n
ts w
e
re p
e
rform
ed
in th
e dark, w
h
ite
l
i
ght a
nd
UV il
l
u
min
a
tions
.
Th
e
forw
ard I-V character
i
stics w
e
re analy
z
e
d
usin
g
stand
ard ther
mi
onic
emiss
i
on re
l
a
tion for el
ectro
n
transport fro
m
Metal-se
mic
o
n
ductor-
meta
l(M
S
M)w
ith low
dopin
g
conce
n
tra
t
ion
.
T
he satur
a
tion curr
ent w
a
s
obtai
ne
d as th
e interc
ept fro
m
the
straig
ht l
i
ne
of ln
I vers
us V, T
.
It
w
a
s found t
hat at
5V, these c
u
rrents
w
e
re 2.45
×
1
0
-5, 5.7
7
×
1
0
-
5
, 6.12×
10-
4
A, respectiv
e
ly
. Also c
har
acte
ristics of th
e M
S
M ph
otod
etec
tor,
line
a
r a
nd lo
ga
rithmic forw
ard
and rev
e
rse b
i
as, at di
fferent ann
eal
in
g
temperatur
es: as-d
epos
ited, 10
0°
C,
200°
C and
300
°C in the dark
mo
de.
Ke
y
w
ords
:
ph
otodetect
o
r, lig
ht and UV il
lu
minati
ons, Ge-lik
e micr
oflow
e
rs,
effect of thermal an
ne
ali
n
g
Copy
right
©
2015 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
A metal–se
mi
con
d
u
c
tor–
m
e
tal photod
etector
(M
SM d
e
tector) i
s
a p
hoto-d
e
tecto
r
device
contai
ning two Schottky
contact
s
,
i.e.,
two metalli
c electrode
s o
n
a semi
con
d
u
ctor
materi
a
l
, in
contrast to
a
p–n ju
nctio
n
as in
a p
hoto
d
iode.
Du
ring
ope
ration,
so
me ele
c
tri
c
v
o
ltage i
s
ap
pl
ied
to the el
ectrode
s. When
light impi
ng
es
on th
e
semico
ndu
cto
r
between
th
e ele
c
tro
d
e
s
, it
gene
rate
s el
ectri
c
carrie
rs (ele
ctron
s
and h
o
le
s)
,
whi
c
h a
r
e
col
l
ected
by the
elect
r
ic fiel
d
and
thus ca
n form a photocu
rre
nt. MSM
detecto
rs
ca
n be made faster than p
hotodio
d
e
s
. Their
detectio
n
b
a
ndwi
d
ths can
re
ach h
und
reds of
gig
a
h
e
rtz, ma
king
them suitabl
e
for
very hi
gh
-
spe
ed o
p
tical
fiber
comm
u
n
icatio
ns.
Co
nsi
s
t of
interd
igitated
metal
lic
ele
c
trode depo
sited on top
of a semi
co
ndu
ctor m
a
te
rial with
whi
c
h it
form
s Schottky con
t
acts
Broad band width, high
sen
s
itivity with a low
ca
pacita
n
ce an
d da
rk
cu
rre
n
t, low cost
of fabri
c
atio
n and
ea
se
of
monolithi
c int
egratio
n
resp
onsivity is lo
w du
e
to th
e sh
ado
win
g
effect ba
ckside ill
uminat
ed
stru
cture
can
be
u
s
ed
or t
h
in
semi
tran
spa
r
ent
ele
c
t
r
ode
s can
be
grown [1, 2]
. Advantage
of
MSM ph
otod
etector
stron
g
ele
c
tri
c
fiel
d in th
e
activ
e
a
r
ea
pu
re
drift ph
otocurrent, n
o
diffu
sion
comp
one
nt
and ve
ry fa
st ph
oto respon
se ,
dete
r
mined
by saturation
vel
o
city, vs. M
S
M
photod
etecto
r ba
sed
on
G
e
na
no
stru
ct
ure
s
Optica
l
detecto
rs a
r
e
appli
ed i
n
all
fields of
hu
man
activities from
basi
c
re
sea
r
ch to com
m
ercial ap
plicatio
ns in commu
nicatio
n
, auto
m
otive, medical
imaging,
hom
eland
se
cu
rit
y
, and othe
r f
i
elds. T
he
fu
n
damental
pu
rpose of a
n
y
photod
etecto
r is
to conve
r
t opt
ical
signal
s in
to electri
c
al
si
gnal
s,
usually expre
s
sed a
s
a p
hoto
c
urrent, whi
c
h
ca
n
be amplified,
displ
a
yed an
d/or ret
r
an
sm
itted. Ge
has
been attra
c
tiv
e
as an alte
rnative sub
s
trate
to Si becau
se Ge ha
s hig
her carrie
r mobility
over Si and goo
d co
mpatibility with Si processi
ng
[3]. Due to its optical pro
p
e
rties, Ge i
s
a good
candi
date for the developme
n
t of light detectors
operating i
n
t
he n
ear infra
r
ed
re
gion
(NIR: 800
-16
0
0
nm) e
s
pe
cia
lly when
inte
gration
with
Si-
based device
s
are
requi
re
d. Homoju
nct
i
on Ge phot
o
d
iode
s ca
n b
e
fabricated
on top of gra
ded
[4] and thin
con
s
tant co
mpositio
n. SixGe1-x/Si
bu
ffer layers [5]. Alternatively, Ge can b
e
depo
sited di
rectly on Si wi
thout any inte
rmedi
ate Si
G
e
layer. Si ca
n then a
c
t bot
h as a
su
bst
r
ate
and a
s
one
of the diode terminal
s. Example
s
are p-i-n h
e
teroj
u
n
c
tion ph
otodi
ode
s ba
sed
on
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
Effect of Therm
a
l Annealing Tem
peratu
r
es on MS
M P
hoto Dete
ctor Based on
… (M. J. Jawad)
503
cry
s
talline [6], poly crystalli
ne and am
orphou
s Ge [7]. In the last two deca
d
e
s
there ha
s be
en
a
stable
re
se
arch i
n
tere
st i
n
t
he develo
p
ment
of hi
gh-spe
ed ph
otodete
c
tors
in the fo
rm
of
rectifying
me
talsemi
c
on
du
ctor-metal
p
hotodet
e
c
tor (MSM
-PD). Based
on
an inte
rdigit
ated
Schottky ba
rrier structu
r
e,
the MSMPD
has a
simp
l
e
device techn
o
logy, low da
rk
curre
n
t, fast
respon
se,
small ca
pa
cita
nce
and l
a
rg
e active a
r
e
a
. Most of t
he be
nefici
a
l
prop
ertie
s
o
f
the
MSM-PD
ste
m
from its la
teral pl
ana
r
geomet
ry.
Th
e co
ntact
s
of
the MSM-P
D
a
r
e from t
w
o
interdigitate
d
,
forkssha
ped
that
functio
n
as ba
ck
-to-ba
ck Sch
o
ttky d
i
ode
s. The
ba
sic structu
r
e
of
the MSM-PD
is illustrated i
n
Figure 1.
Figure 1. A schem
atic ima
ge
of an MSM photodio
d
e
stru
cture
One of th
e
advantag
es
of the inte
rdi
g
itat
ed MSM
detect
o
r i
s
that finger width and
spa
c
in
g as well as the ligh
t
sensitive area ca
n easily
be adjuste
d with a simpl
e
mask
cha
n
g
e
.
Some expe
ri
mental a
nd t
heoretical
re
sults
dem
on
strating respo
n
se tim
e
de
p
ende
nce on
the
MSM-PD ge
o
m
etry has al
ready bee
n re
ported in the
past [8, 9].
2. Theor
y
The devi
c
e
works by a
b
sorbing opti
c
al e
nergy
a
nd
co
nverting a
ph
oton flux into a time
varying el
ect
r
ical
sig
nal.
When th
e a
c
tive a
r
ea
s
of th
e devi
c
e
are
unde
r illu
min
a
tion, carriers in
the se
micon
ducto
r a
b
so
rption layer (also
kn
own
as el
ect
r
onh
ole pai
rs) a
r
e gen
erate
d
by
incid
ent p
hot
ons havin
g e
nergy
greater than th
e b
a
n
dgap
en
ergy.
The
carriers
are t
r
an
sp
ort
ed
to the metal conta
c
t pad
s,
and a cu
rre
n
t
is detec
ted i
n
the externa
l
circuit unde
r the applicati
o
n
of an externa
l
bias voltage
.When a voltage is exte
rn
ally applied o
n
two electro
des sy
stem, it
biases them
so that one is in t
he forward and the oth
e
r is in the re
verse di
re
ctio
n. A compari
s
on
of the energy
band di
agram
of Schottky and MSM
phot
odete
c
tor is ill
ustrate
d
in Fi
gure 2.
Figure 2. Energy band di
ag
ram of (a
) Scho
ttky photod
etector
and (b) MSM phot
odete
c
tor at
zero bia
s
, an
d (c) MSM ph
otodete
c
tor at
moderate bia
s
Whe
n
the bi
a
s
voltage i
s
zero, Schottky
photodi
ode
p
r
odu
ce
s a
certain amou
nt o
f
photo curre
n
t
and the ele
c
tric field is ze
ro at the cent
er sin
c
e the
structu
r
e of the MS
M is symmetrical. Photo-
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ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 16, No. 3, Dece
mb
er 201
5 : 502 – 508
504
excited el
ectrons
are t
r
app
ed in the p
o
te
ntial well a
nd
the net ph
oto
c
urre
nt is
zero (Fig
ure
2(b
)
).
Whe
n
the bi
a
s
is mod
e
rate
, the potential
barrie
r
at
the
forward
co
ntact is de
crea
sed
as
sh
own
in
Figure 2(c).
There is an
electri
c
fiel
d betwe
en the Sch
o
ttky electrode
s.
The majo
rity of
photoel
ectron
s a
r
e trapp
ed
in the
potent
ial well
an
d the ph
oto-hol
es a
r
e
not, b
u
t ca
nnot le
a
v
e
the active
re
gion b
e
cau
s
e
of the charg
e
of the
tra
p
p
ed ele
c
trons.
The n
e
t phot
ocu
r
rent is v
e
ry
small.
Whe
n
the bia
s
i
s
raised, the
p
o
tential
ba
rri
er fo
r ph
otoe
lectro
ns di
sa
ppea
rs an
d the
depletio
n reg
i
on will
be
wi
dene
d an
d e
v
entually
be
comes eq
ual t
o
ele
c
tro
de
separation. T
h
e
carrie
r tran
sp
ort mechani
sm is simila
r
as in
Schottky photodi
od
e by the transp
o
rt of ph
oto-
gene
rated el
ectro
n
s from
the semi
con
ducto
r to
the
metal over the potential
barrier a
nd t
he
carriers inject
ion from the
meta
l into
th
e semi
cond
u
c
tor which
co
ntribute
to th
e da
rk
curre
n
t
.
A
photon
with
e
nergy
greater than th
e b
a
n
dgap
will
be
absorb
ed
by
an el
ectron
e
x
citing it to
th
e
con
d
u
c
tion b
and. The mo
st important
feature
s
of any photodete
c
tor a
r
e rep
r
ese
n
ted by the
respon
sivity, quantum
efficien
cy, re
sp
o
n
se
time
se
ri
es
re
sista
n
ce
, cont
rast
rat
i
o an
d
curre
n
t
gain. To stu
d
y
the effective Schottky b
a
rri
er hei
ght SBH, the famous m
odel th
at can be u
s
e
d
to
determi
ne cu
rre
nt-voltage
(I-V)
ch
ara
c
t
e
risti
c
s
is
the
thermi
onic e
m
issi
on th
eory, Acco
rdin
g
to
this theory, th
e curre
n
t (Id)
from the se
mi
con
d
u
c
tor to the metal ca
n be expre
s
sed
as:
(
1
)
Whe
r
e n i
s
the ideality fa
ctor
whi
c
h m
a
y
depen
d o
n
temperature and in
depe
ndent on volt
age,
Vd is the voltage a
c
ro
ss the diod
e, k is the Bolt
zma
n
con
s
tant, a
nd Io is the saturation
cu
rrent
given by:
(
2
)
Whe
r
e
q i
s
the el
ect
r
on
charg
e
, T
the
temperatur
e,
A
is
th
e co
ntact
a
r
e
a
, A** is the effective
Richardson consta
nt and (
φ
b
) is the Sch
o
ttky barri
er h
e
ight.
Equatio
n (1) at V>3kT/q, becom
e:
(
3
)
The th
eoretical value
of
A*
*
can be cal
c
ulated usi
ng
A*
* =
4
m*
qk2/h
3
a
nd
b
a
se
d o
n
the effective
mass
m*
. The plot of ln
I vs V will
give
a st
raight li
n
e
with
a sl
op
e of q/(nkT
),
and
the intercept
with y-axis will yi
eld Io,
in which barrier height,
φ
b can be o
b
t
ained by usi
ng
Equation
(2)
and the id
eal
ity factor fro
m
the sl
o
pe.
A top view
of SEM imag
e of PS sam
p
le
prep
ared ove
r
30 mi
n et
chi
ng time i
s
sh
own i
n
Fig
u
re
4(a
)
. Fo
r this sam
p
le, which is p
r
e
pared
at
the optimi
z
ed
co
ndition,
a
uniform
di
stri
bution of
po
res with si
ze
of
100
~2
00 n
m
was
ide
n
tified.
A side view
o
f
the poro
u
s
netwo
rk
cross section
i
ndi
cate
s that the
dimen
s
ion
a
l length is
ran
g
ed
from 85 to
95
μ
m as ill
ust
r
ated in Fi
gure 3(b). Th
e g
r
owth
of Ge fi
lm wa
s o
b
tai
ned by a
sim
p
le
and lo
w-co
st
ECD te
chni
que, where this meth
od y
i
elded a l
a
rg
e are
a
of Ge
microstructu
res.
Figure 3
(
c) a
nd (d)
re
pre
s
ent re
sp
ectiv
e
ly, low a
nd
high m
agni
-fication
SEM i
m
age
s fo
r th
e
entangl
ed Ge
micro
r
o
d
s in
low dime
nsi
ons that
form
ed on the Si. The len
g
ths
of the microrods
were ab
out several mi
cron
s and
had a
n
avera
ge
di
ameter of a
b
out 500
~20
0
nm. Figure 3
(
e)
illustrate
s a typical SEM image in lo
w magnificati
o
n
of Ge microsp
heres
with nano
wires
net
gro
w
n
on PS
sub
s
trate.
Th
e di
stributio
n
extends to
co
ver the
wh
ole
su
rfa
c
e of
G
e
micro
s
p
heres
with a
dia
m
et
er
of ab
out 5
00 n
m
. Figu
re 3
(
f)
sho
w
s
a typical
hig
h
-
mag
n
ificatio
n SEM ima
g
e
with
more detail
s
of the net formed und
er th
e Ge micros
p
here
s
. This n
e
t has dimen
s
ion
s
of less than
100 nm in
di
ameter a
nd a
length of ab
out few mi
cro
n
s. The E
D
X on the top ri
g
h
t of Figure
3
(
c)
and Figu
re 3
(
e)
confirm
e
d
the gro
w
th of
Ge
on
bot
h sub
s
trate
s
.
The
results
sho
w
e
d
that
the
amount of O
wa
s found to
be very low relative to the existing Ge.
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TELKOM
NIKA
ISSN:
2302-4
046
Effect of Therm
a
l Annealing Tem
peratu
r
es on MS
M P
hoto Dete
ctor Based on
… (M. J. Jawad)
505
Figure 3. SEM image
s (a
) surfa
c
e of PS
sample,
(b)
cross
se
ction of PS sample
, (c) lo
w and
(d)
high mag
n
ification SEM image
s of Ge m
i
cro
r
o
d
s o
n
Si, (e) micro
s
ph
ere
s
with na
n
o
wires in lo
w
magnification
and (f) hig
h
magnification
of Ge nano
wires o
n
PS
The
Ge
micro
s
ph
ere
s
were
clo
s
ely
attached
with
the
PS sub
s
trate
as
sh
own in
t
he SEM
image
of Figu
re 3
(
e
)
. Thi
s
coul
d be
attri
buted to th
e p
a
rtial filling
of the Ge
parti
cl
es in
the p
o
re
s,
and thu
s
lea
d
to improve
the stru
ctu
r
al
stability
of the porou
s sili
con su
bst
r
ate.
Hen
c
e, the
PS
surfa
c
e h
ad a
significant effect on t
he si
ze and shap
e of the Ge nan
owires.
3. Discus
s
the
Resul
t
s
The Schottky
barrier
heig
h
t
s and i
dealit
y factor
were
cal
c
ulate
d
from Equatio
n
(2)
and
(3). In a
dditio
n
, the se
rie
s
resi
stan
ce,
contra
st
ratio,
and the
cu
rre
n
t gain. All th
ese
cal
c
ul
atio
ns
were ca
rri
ed
out for the
as-grown an
d anneal
ed
MSM photod
etectors in white light and
UV
illumination and the results
are listed in
Table 1.
Table 1. Barri
e
r heig
h
t, ideality factor, serie
s
re
si
stan
ce, co
ntra
st ratio and curre
n
t gain for as
gro
w
n an
d an
neale
d
MSM photod
etecto
rs mea
s
u
r
ed u
nder
white lig
ht and UV illu
mination
s
.
Temp.
(
˚
C)
Photodetectors
Barri
er
height
φ
b (eV
)
Ideality
factor n
Series
resistance
R (k
Ω
)
Contrast
Ratio at 5V
Curre
nt
gain
A
s
g
r
ow
n
Light 0.725
1.46
81.37
2.35
10
UV 0.672
1.1
8.34
24.9
50
100
Light 0.707
1.31
40.7
11.75
20
UV 0.662
1.0
5.56
93.5
75
200
Light 0.684
1.19
16.3
47
50
UV 0.636
0.9
2.08
398.8
200
300
Light 0.693
1.2
23.3
41.15
35
UV 0.644
1.03
2.78
373.8
150
Anneale
d
sa
mples exhibit
ed mo
re
sig
n
ificant
cha
n
ge
comp
are
d
to the a
s
d
e
posite
d
MSM photo
d
e
tector.
It was
ob
serve
d
that the
barrier hei
ght a
nd
the
ide
a
lity factor fo
r
the
detecto
r de
creased with i
n
crea
si
ng te
mperature
u
n
til 200°
C then st
a
r
ted to
rise a
gain.
The
barrier hei
ght
de
cre
a
ses from 0.72
5 eV
to 0.684
eV
with the
in
cid
ent white ligh
t
and from
0.672
to 0.636
eV with UV light
when the
te
mp
eratu
r
e i
s
ele
v
ated from
25
to 200
˚
C,
accomp
anie
d
b
y
a
notice
able i
m
provem
ent of
the id
eality factor n
whi
c
h
de
cre
a
ses from 1.46
to 1
.
19 an
d 1.1
to
0.9, re
spe
c
tiv
e
ly. The
co
ntrast
ratio, rep
r
ese
n
ted
by th
e ratio
of
pho
tocurre
n
t to t
he d
a
rk
cu
rre
n
t
at 5V, which
wa
s
cal
c
ul
a
t
ed for an
ne
aled
sam
p
le
s a
nd fo
und
to in
crea
se
with i
n
crea
sing
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TELKOM
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Vol. 16, No. 3, Dece
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er 201
5 : 502 – 508
506
temperature
with valu
es
of 47
and
398
at 200
°C for white
light a
nd
UV illumin
a
tions,
respe
c
tively. The m
a
ximu
m current
gai
ns
of the
dev
ice
s
in
crea
se
d at a
nne
alin
g temp
eratu
r
es
up to 200
˚
C i
n
both white light and UV
illumination
s
.
Th
is could b
e
due to the
redu
ction
of the
seri
es resi
sta
n
ce
a
s
a
fun
c
tion of a
nne
al
ing temp
erature
up
to 2
0
0
˚
C. Su
ch
a
re
sult
cont
ribut
es
to low dark current from th
e Schottky ba
rrie
r
MSM ph
otodete
c
tors.
Figure 4. Cha
r
acte
ri
stics of
the as grown
MSM photod
etector
based
on Ge like mi
croflo
we
rs
unde
r da
rk, white light and
UV illuminatio
ns
From Fi
gure
4, the re
spo
n
se
of the Pd
MSM phot
odete
c
tor in
crea
se
s with t
he bia
s
voltage an
d it
satu
rate
s g
r
adually
whe
n
the voltage
i
s
b
e
yond
2V. The
cu
rrent
starting
at a
l
o
w
voltage is typical of th
ermi
onic emi
ssi
o
n
curren
t. In
the linea
r
reg
i
on, the the
r
mionic emi
ssi
on
and the carri
e
r velocity increa
se with th
e biasi
ng voltage. The da
rk cu
rr
ent and
the photocurrent
are
satu
rated
becau
se all
carrie
rs
are swept o
u
t
toward
s the
co
ntacts. It can b
e
noticed that
the
MSM photod
etector
prod
uce
s
lo
we
r d
a
rk
cu
rrent
than that of t
hose of white light an
d
UV
illuminations
at 5V bias. This shows that the light
illu
mination can
effectivel
y create electron-hole
pairs in
Ge and greatly increase
the carrier
density. Under illumi
nation, light im
pinges onto the
Ge layer, th
e
high e
nergy photon
s a
r
e
absorb
ed
b
y
this layer
prod
uci
ng m
o
re el
ect
r
on
-hole
pairs, the
ap
plicatio
n of
a
bia
s
voltag
e
to the
Pd
contact
create
s
a
n
el
ect
r
ic field
within t
he
unde
rlying G
e
layer that sweep
s the
photo ge
ner
ated ca
rri
ers out of the
depletio
n reg
i
on,
resulting in a
n
increa
se of the photo
c
urrent with voltage.
Figure 5. Cha
r
acte
ri
stics of t
he MSM photodete
c
tor, (a) linea
r an
d (b) lo
garith
m
i
c
forward and
reverse bi
as,
at different an
nealin
g temp
eratu
r
e
s
: as-depo
sited, 10
0°C, 20
0°
C a
nd 300
°C in t
he
dark mod
e
Figures 5(a) and
(b
)
sh
ow lin
ea
r a
nd log
a
rithmi
c forwa
r
d
a
nd reverse
bias I-V
cha
r
a
c
teri
stics of Pd MSM
photod
etecto
r anneale
d
at 100, 200 an
d
300°C tog
e
ther with that for
the a
s
-depo
si
ted dio
de,
wh
ere
all m
e
a
s
urem
ents we
re
ca
rri
ed
out
in th
e d
a
rk
mode. T
h
e
d
a
rk
curre
n
t exhib
i
ted rem
a
rka
b
le de
pen
de
nce
on th
e
anne
aling te
mperature. T
he da
rk current,
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TELKOM
NIKA
ISSN:
2302-4
046
Effect of Therm
a
l Annealing Tem
peratu
r
es on MS
M P
hoto Dete
ctor Based on
… (M. J. Jawad)
507
whi
c
h is on
e of the main sou
r
ces o
f
noise in photodete
c
tors, decre
ases
with increa
si
ng
anne
aling te
mperature. T
he re
sult
s al
so indi
cate
d optimum I-V
cha
r
a
c
teri
stics esta
blished
by
the lowe
st reverse lea
k
a
ge cu
rrent were a
c
hieve
d
in the sam
p
le anne
aled
at 300°C. T
h
e
variation of th
e Schottky ba
rrie
r
hei
ght wi
th anneal
i
ng tempe
r
ature for Pd Sch
o
ttky contact
s
wit
h
Ge i
s
d
e
mon
s
trated
in
Fig
u
re
5. Th
e S
B
H for a
s
-g
rown
an
d an
n
ealed
sample
s fo
r the
MSM
photod
etecto
r were fou
nd
to vary from 0.779 to
0.820 eV according to the alteration of the
anne
aling te
mperature.
Figure 6. The
depen
den
ce
of Schottky b
a
rri
er
hei
ght on ann
ealing
temperature f
o
r the MSM
photod
etecto
r
It was foun
d
that unde
r dark conditio
n
mea
s
urem
ents, the Schottky co
ntact barrie
r
height of the
MSM photo
detecto
r in
creases
with
in
cre
a
si
ng an
n
ealing temp
e
r
ature within
th
e
rang
e
betwe
en 2
5
-300°
C due
to th
e
lowe
r
dark
cu
rrents exhib
i
ted by th
e t
herm
a
lly-tre
ated
sampl
e
s com
pare
d
to th
at of the
as d
epo
sit
ed
sa
mple. With
such
ob
se
rvations un
der d
a
rk
con
d
ition
s
, the ele
c
tri
c
al
chara
c
te
risti
c
s of the
ph
oto
detecto
r i
s
sa
id to be e
nha
nce
d
by the h
i
gh
temperature
whi
c
h chan
g
e
s Ge n
ano
cry
s
tallites
la
yer bene
ath
the conta
c
t
to single/p
o
ly
cry
s
talline a
nd p
r
omotin
g goo
d ele
c
t
r
ical
condu
ct
ion. Neve
rth
e
less, p
r
evio
us
studie
s
h
a
ve
sho
w
n th
e variation of b
a
rrier hei
ght is
nearly
con
s
ta
nt betwe
en 1
00-5
00°
C . A
n
increm
ent in
the Pd/Ge Schottky conta
c
ts ideality factor
wi
th incre
a
si
ng ann
ealing tempe
r
ature within
the
rang
e bet
we
en 25
-30
0
°
C
can
be
seen
in Figu
re 7.
Such b
ehavi
o
r is i
n
go
od
agre
e
me
nt with
previou
s
work publi
s
h
ed el
se
whe
r
e.
Figure 7. A graphi
cal re
pre
s
entatio
n of the idealit
y factor as a fun
c
ti
on of anne
ali
ng tempe
r
atu
r
e
for the MSM photod
etecto
r
4. Conclu
sion
The p
hotoel
ectri
c
p
r
op
erties of G
e
-li
k
e mi
croflowers grown o
n
Si we
re
studied a
t
different an
n
ealing tem
perature
s
of 10
0
,
200 and
30
0°C in
dark,
white an
d UV
illumination.
The
anne
aled sa
mples exhibit
ed
mo
re sign
ificant
c
han
g
e
s
comp
ared
to the as-g
rown
one. It wa
s
also
ob
se
rve
d
that the
b
a
rri
er
heig
h
t
and th
e id
e
a
lity factor of
the dete
c
tor
decrea
s
e
d
wi
th
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ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 16, No. 3, Dece
mb
er 201
5 : 502 – 508
508
increa
sing
te
mperature
un
til 117, 20
0°
C. The
resp
o
n
sivity displa
yed two
pea
ks, the m
a
xim
u
m
one at 400
n
m
and the se
con
d
lower p
eak at 50
0 n
m
. The rise time of the ph
otodete
c
tor
was
130 m
s
fo
r
4
60 nm
an
d 1
00 m
s
fo
r 4
0
5
nm
and
the
qua
ntum effi
cien
cy
wa
s 1
3
.61% for 40
0 nm
at 5V.
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ces
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y
n
a
m
ic beh
avior
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e
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ductor– meta
l
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i
t
h
sub-
half-m
i
cron e
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ectrod
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