Supplementary Data
Tunneling-based rectification and photoresponsivity in two-
dimensional van der Waals heterostructure devices
Amir Muhammad Afzala, b,*, Yasir Javedc, Naveed Akhtar Shadd, Muhammad Zahir
Iqbale,#, Ghulam Dastgeer b, M. Munir Sajidd, Sohail Mumtaza
aDepartment of Electrical and Biological Physics, Kwangwoon University, Seoul, 01897, Republic of
Korea, bDepartment of Physics & Astronomy and Graphene Research Institute, Sejong University, Seoul
05006, Korea, cDepartment of Physics, University of Agriculture, Faisalabad,38000 Pakistan, dDepartment
of Physics, GC University, Faisalabad, 38000 Pakistan, eNanotechnology Research Laboratory, Faculty of
Engineering Sciences, GIK Institute of Engineering Sciences and Technology, Topi 23640, Khyber
Pakhtunkhwa, Pakistan
*,#Corresponding Authors:
E-mail: *[email protected], #[email protected]
Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2020
Figure S1 (a) Atomic force microscopy image of the final device. The h-BN is sandwiched
between the BP and ReSe2 flakes. The blue and green line shows the BP (bottom) and ReSe2
(top) flakes respectively (b) Height profile of h-BN and ReSe2. The height of h-BN and ReSe2
are 0.91 nm and 10 nm respectively (c) Height profile of BP. The height of BP is 5.8 nm.
(a)
0 1 2 3 4 50
3
6
9
12
15
10 nm
Heig
ht (n
m)
Distance (m)
h-BN + ReSe2
0.91 nm
(b)
0.0 0.5 1.0 1.5 2.0-1
0
1
2
3
4
5
6
7
Heig
ht (n
m)
Distance (m)
BP(c)
5.8 nm
Figure S2 Raman shift of few-layer h-BN.
1200 1300 1400 15000.3
0.6
0.9
1.2
1.5
Inte
nsity
(a.u
)
Raman shift (cm-1)
h-BN
Figure S3 (a) KPFM image of BP flake to find the work function. The work function of few-layer
BP is 4.5 eV (b) KPFM image of ReSe2 flake. The work function of ReSe2 is 5.12 eV.
Figure S4. Schottky barrier of ReSe2 device using Sc/Au contacts (a) Current-voltage curves of
ReSe2 device with Sc/Au contacts in semi-log plot. Inset figure shows Current-voltage curves of
ReSe2 device (b) Richardson’s plot ln (I/T2) versus q/KBT of ReSe2 heterostructure device with
Sc/Au and Cr/Au contacts.
(a) (b)
0.0 0.5 1.0 1.5 2.010-7
10-6
10-5
10-4
Curre
nt (A
)
Voltage (V)
300 K 250 K 200 K 175 K 150 K 100 K 0.0 0.5 1.0 1.5 2.0
10-8
10-7
10-6
10-5
Curre
nt (A
)
Voltage (V)
300 K 250 K 200 K 175 K 150 K 100 K
Cr/Au
Sc/Au(a)
30 40 50 60 70 80 90-30
-29
-28
-27
-26
-25
-24
98.4 meV
Cr/Au Sc/Au
Ln (I
/T2 )
q/KbT
37 meV
(b)
Figure S5 (a) Ids-Vds curves of p-BP at different lengths at Vbg = -60 V. Inset figure shows the Ids-
Vds curves of n-ReSe2 at different lengths at Vbg = 60 V (b) Contact resistance of BP and ReSe2 (c)
Band diagram of metal (Sc) and TMDs material (n-ReSe2) Ohmic contact in which
(d) Band diagram of metal (Cr) and TMDs material (p-BP) Ohmic contact in which 𝜙𝑆𝑐 < 𝜙𝑅𝑒𝑆𝑒2
.𝜙𝐶𝑟 ≥ 𝜙𝐵𝑃
(d)(c)
Figure S6 Current-Voltage (Ids-Vds) curves in linear plot measured across the BP/ReSe2 diode
with thickness (5.9 nm/10 nm) at various back gate voltage from -60 V to + 60 V. At this thickness,
it shows p-n characteristics.
Figure S7 Gate-dependent rectifying effect of the BP/h-BN/ReSe2 heterojunction diode in a linear
scale as a function of back-gate voltage.
-5 -4 -3 -2 -1 0 1 2 3 4 50
100
200
300
400
500
-60 V -30 V -45 V -15 V 0 V 15 V 30 V 45 V 60 V
I ds (
A)
Vds (V)
with hBN
Vbg =
Figure S8 Procedure of calculating the Ideality factor of the BP/ReSe2 vdW heterojunction (𝜂)
diode. First, we plotted the Ids-Vds curves in semi logarithmic scale then fitting the data in the small
forward biased region.
Figure S9 Temperature-dependent Ids-Vds cures in a linear scale of heterojunction device
-4 -3 -2 -1 0 1 2 3 4
0
5
10
15
20
25
I ds (
A)
Vds (V)
50K 100 K 150 K 200 K 250 K 300 K
0 1 2 3 4 5-24
-21
-18
-15
-12
-9
-6
Current Fitting line
Ln (I
)
Vds (V)
Vbg = 0 V
Figure S10 Stability of the devices (a) Rectifying current behavior of BP/h-BN/ReSe2
heterojunction device. Inset figure shows the rectifying behavior without h-BN (b) Comparison of
the devices with h-BN and without h-BN. The performance of the device without h-BN decreased
more rapidly due to oxidation.
Figure S11 Change in rectification ratio with the number of layers of h-BN (a) Ids-Vds curves in
log scale at fixed back gate voltage -60 V with h-BN and without h-BN in BP/ReSe2 heterojunction
p-n diode (b) Change in rectification ratio with number of layers of h-BN.
-6 -4 -2 0 2 4 61E-15
1E-13
1E-11
1E-9
1E-7
1E-5
I ds (A
)
Vds (V)
Without h-BN Monolayer h-BN Bilayer h-BN Trilayer h-BN
(a)
0 1 2 3106
107
108
Rect
ifica
tion
ratio
Number of layer
(b)
0 5 10 15104
105
106
107
108
Rect
ifica
tion
ratio
Number of day
Device with h-BN Device without h-BN
(b)
-6 -4 -2 0 2 4 610-14
10-12
10-10
10-8
10-6
10-4
10-2
100
I ds (A
)
Vds (V)
0 day 5 day 10 day 15 dayVbg = -60 V
(a)
-6 -4 -2 0 2 4 610-12
10-10
10-8
10-6
10-4
10-2
I ds (A
)
Vds (V)
Without h-BN
Vbg = -60 V
Rectification ratio is increased in case of h-BN. Further, the RR depends on the thickness of h-BN.
In monolayer case, the RR is small due to DT at low bias and DT & FNT at high bias. But in case
of higher thickness, the h-BN also shows ratification. At low bias, the charge carrier blocked and
gives to rise a small leakage current.
Figure S12 Esaki diode behavior at various back gate voltage from -60 V to + 60 V with the
thickness (30 nm/39 nm)
Figure S13 Backward diode characteristics at various back gate with the thickness (65 nm/32 nm)
Figure S14 (a) Rectification ratio of heterojunction diode of different samples at the fixed back
gate -60 V. (b) Rectification ratio of heterojunction diode of different samples at the fixed back
gate -60 V with h-BN
Figure S15 Photon-current as a function of the power of the incident laser at different back-gate
voltages from 60 V to -60 V with step size 15 V of heterostructure device at VDS = −2V
100 200 300 400 500
80
120
160
200
240
I ph (n
A)
PLaser (mWcm-2)
-60 -45 -30 -15 0 15 30 45 60
Vbg =
Figure S16 Photocurrent of heterostructure device under the laser light source with different
powers . The photo-current is raised and declined exponentially when (𝑃 = 40, 50, 60, 70, 80 𝜇𝑊)
the light turned ON and OFF respectively (b) Fitting procedure to calculate the rise and decay time
0 48 96 144 192 240
0
100
200
300
400
500
OFF
I ph (n
A)
Time (Sec)
80 W 70 W 60 W 50 W 40 W
ON
without h-BN
(a)
0 48 96 144 192 240
0
100
200
300
400
500
600 40 W 50 W 60 W
70 W 80 W
I ph(n
A)
Time (Sec)
withh-BN
110 120 130 140 150 160 170
0
200
400
600
I ph (n
A)
Time (Sec)
Photocurrent Fitting line
(b)
80 100 120 140
0
100
200
300
400
500 Photocurrent Fitting line
I ph (n
A)
Time (Sec)
p-n & p-i-n
Thickness(nm)
Rectificationratio (RR) 𝜂 𝜆1/𝜆2
(mS)Voc(V)
Isc(nA)
R(mA/W)
D(Jones)
EQE (%)
BP/ReSe2 5.9/10 >106 1.22 60/230 0.51 223 7.5 2.3 × 1012 2.09BP/h-
BN/ReSe26/.91/10 107 1.065 49/180 0.58 241 12 18.9 × 10122.79
= ideality factor, rise and decay time, Voc = open-circuit voltage, Isc = short-circuit 𝜂 𝜆1/𝜆2 =
current, D = detectivity, R = responsivity, EQE = external quantum efficiency
Table 1. Comparison of important parameters for the heterostructure devices with h-BN and
without h-BN
p/nheterostructur
e
Thickness(nm)
Rectification
ratio (RR)
Idealityfactor
Responsivity
(mA/W)
EQE (%)
Reference
WSe2/MoS2 0.8/0.8 --- --- 10 --- 1
BP/MoS2 11/0.8 105 2.7 11 0.3 2
BP/BP 8.5 103 1 3
BP/WeSe2 20/12 103 --- 3.1 4
WSe2/MoS2 25/18 106 1.5 170 --- 5
MoS2/MoTe2 2/5 103 --- --- --- 6
MoS2/WSe2 0.65/0.7 50 --- 11 1.5 7
BP/ReS2 5/12 106 1.04 8 0.3 8
BP/ReSe2 (This work)
5.9/10 >106 1.22 7.5 2.09
BP/h-BN/ReSe2
(This work)
6/.91/10 107 1.065 12 2.79
EQE = external quantum efficiency
Table 2. Comparison of key parameters such as rectification ratio, ideality factor, responsivity,
external quantum efficiency with previously reported values in TMDs based devices.
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