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: *a.m.afzal461@gmail.com, #zahir.upc@gmail.com

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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