반도체 개론
(Introduction to Semiconductor)
Subject : CHE3308-001
Time (Class room) : 수 (60주년 106), 목 ( 5E110) 13~15교시
박동혁
화학공학과
donghyuk@inha.ac.kr
1
Field Effect Transistors
source
gate electrode
gate dielectric
drain
pentacene
thin film FET
Conducting
layer
Schoonveld et al
Nature 2000
Molecular material
2
Working principles of FETs
3
Operating Principle of FET - I
VG=VS=VD=0
+
+
Source
+
+
+
+
+
+
Insulator
+
+
+
Drain
+
+
Source
+
+
+ + + + + + + + +
+
Insulator
Gate
+
Drain
- - - - - - - - - - - - Gate
VD=VS=0, VG>0
VS=VD=0, VG<0
+
+
Source
+
+
+ + + + + + + + +
+
Drain
Insulator
+ + + + + + + + + + + + + +
Gate
+
Operating Principle of FET - II
VG=VS=0,VD<0
+
+
Source
+
+
+
+
+
+
+
VS=0, VG<VD<0
+
+
Drain
+
+
+
Source
+
+
+
Drain
+ ++ + ++
+
Source
- - - - - - -
+
+
++ + +
- - -
+ + +
+ ++ + ++ + +
Gate
I
I
V
+
+
Drain
Insulator
Gate
Gate
V
+
Insulator
Insulator
I
+
+
VS=0,
VD<VG<0
V
Current-Voltage (I-V) Characteristics
6
p-type organic semiconductors
7
n-type organic semiconductors
8
Evolution of OFET- I
OFET at beginning stage
Top contact
• active : vapor deposited
pentacene film
• mobility μ= 1.23 cm2/Vs , Ion/off = 1.8 *107
Ref. Adv. mater. 14, 99 (2002)
Bottom contact
• active : vapor deposited
pentacene film
• mobility μ(left)= 0.48 cm2/Vs, μ(right)= 0.30 cm2/Vs
Ref. Synth. met. 18, 609 (1987)
Synth. met. 25, 11(1988)
- H. Koezuka, A. Tsumura, and T. Ando
Ref. Adv. mater. 19, 371(2007)
9
Evolution of OFET- II
Active Materials
small molecules, polymers, organic crystals
Small molecules
Polymers
Organic single crystals
• pentacene, phtalocyanine, rubrene, etc.
• P3HT, PQT-12, etc.
• rubrene, pentacene, C60, etc.
• vacuum deposited pentacene:
mobility μ= 3.3 cm2/Vs, Ion/off =1.5*106
• solution-processed PQT-12:
mobility μ=0.07~0.12 cm2/Vs, Ion/off >106
• vacuum deposited phtalocyanine:
mobility μ= 0.02 cm2/Vs, Ion/off =4*105
• solution-processed P3HT:
mobility μ=0.1 cm2/Vs, Ion/off >106
• rubrene single crystal:
mobility μ=2.4 cm2/Vs, Ion/off >107
• pentacene single crystal:
mobility μ=0.2 cm2/Vs, Ion/off ~106
• solution-processed rubrene:
mobility μ= 1.23 cm2/Vs, Ion/off >106
Ref. J. Phys. Chem. B 107, 5877 (2003)
Appl. Phys. Lett. 69, 3066 (1996)
Adv. mater. 19, 2624 (2007)
Ref. J. Am. Chem. Soc. 126, 3378 (2004)
Science 280, 1741 (1998)
Ref. Nature 444, 913 (2006) 10
Pentacene
11
Pentacene
Molecule of Pentacene
Vacuum
pentacene
2.9
-6T
2.9
C60
5.1
Au
5.1
3.8(LUMO)
5.2
HOMO
7.1
12
Mobilities for Different Phase of Pentacene
Crystallinity
Amorphous
Polycrystal
Single Crystal
- C.D. Dimitrakopoulos, D.J. Mascaro, IBM J. Res. & Dev. 45. 11 (2001).
13
Pentacene Derivatives
Synthetic procedure to afford trialkylsilylethynyl substituted
pentacene derivative
14
Perfluoropentacene
15
Perfluoropentacene: High-Performance p n Junctions and
Complementary Circuits with Pentacene
16
Perfluoropentacene: High-Performance p n Junctions and
Complementary Circuits with Pentacene
Molecular packing diagrams of (a)
pentacene and (b) perfluoropentacene.
(a) Structure of a perfluoropentacene OFET. (b) Drain current
(ID) versus drain voltage (VD) characteristics as a function of
gate voltage (VG) for a perfluoropentacene OFET on OTSmodified SiO2 (Tsub=50 °C). (c) ID and ID1/2 versus VG plots at
VD =40 V for the same device. The field-effect mobility
calculated in the saturation regime is 0.11 cm2/Vs.
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Perfluoropentacene: High-Performance p n Junctions and
Complementary Circuits with Pentacene
Absorption and Emission spectra of pentacene and perfluoropentacene in 1,2dichlorobenzene.
18
Perfluoropentacene: High-Performance p n Junctions and
Complementary Circuits with Pentacene
Energy diagrams calculated level for pentacene and perfluoropentacene.
19
Perfluoropentacene: High-Performance p n Junctions and
Complementary Circuits with Pentacene
(a) Structure of a perfluoropentacene/pentacene bipolar OFET. (b) Drain current (ID) versus gate
voltage (VG) characteristics at drain voltages VD= -40 and 40 V for a perfluoropentacene
/pentacene bipolar OFET. The field-effect mobilities are calculated to be 0.024 and 0.035 cm2/Vs
for the n- and p-channel operations, respectively.
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Ambipolar organic field-effect transistors
21
Ambipolar transport in donor/acceptor mixtures
22
Photoactive Organic Transistor
Categorization of photoactive organic field-effect transistors (OFETs).
23
Nanowires Applications
“Bottom-up” to form nanowire diodes
• Schottky diodes can be formed by contacting a
GaN nanowire with Al electrodes.
•
p-n junction diodes can be formed at the crossin
g of two nanowires, such as the crossing of n and
p-type InP nanowires doped by Te and Zn, or Si n
anowires doped by phosphorus (n-type) and boro
n (p-type).
Nanowire logic gates:
(a) Schematic of logic
OR gate constructed
from a 2(p-Si) by
1(n-GaN) crossed
nanowire junction.
The inset shows the
SEM image (bar:
1μm)
(b) The output voltage
of the circuit in (a)
versus the four
possible logic
address level inputs
( logic 0 input is 0V
and logic 1 is 5V).
(c) Schematic of logic AND gate constructed from a 1(p-Si) by 3(n- GaN)
crossed nanowire junction. The inset shows the SEM image (bar: 1μm)
of an assembled AND gate and the symbolic electronic circuit. (d) The
output voltage of the circuit in (c) versus the four possible logic
address level inputs
Nanowires
• In addition to the crossing of two distinctive nan
owires, heterogeneous junctions have also been c
onstructed inside a singlewire, either along the wi
re axis in the form of a nanowire superlattice or p
erpendicular to the wire axis by forming a core-sh
ell structure of silicon and germanium.
• These various nanowire junctions not only posses
s similar current rectifying properties as expected
for bulk semiconductor devices, but they also exhi
bit electro-luminescence (EL) as of a crossed junct
ion of n and p-type InP nanowires that may be in
teresting for optoelectronic applications.
Optical Properties of Nanowires
Light emission from quantum wire p-n junctions is
especially interesting for laser applications, because :
• quantum wires can form lasers with lower excitation th
resholds compared to their bulk counterparts, and
• they also exhibit a decreased temperature sensitivity in
their performance.
• Furthermore, the emission wavelength can be tuned fo
r a given material composition by only altering the ge
ometry of the wire.
Light emitting diodes (LEDs) achieved in junctions
between a p-type and an n-type nanowire
Fig. 4.39a,b Optoelectrical characterization of a crossed nanowire junction
formed between 65-nm n-type and 68-nm p-type InP nanowires. (a)
Electroluminescence (EL) image of the light emitted from a forwardbiased nanowire p-n junction at 2.5V. Inset, photoluminescence (PL)
image of the junction. (b) EL intensity as a function of operation voltage.
Inset, the SEM image and the I–V characteristics of the junction.
Field Effect Transistors
The structure of a conventional unipolar OFET. The organic transport material is separated
from the gate electrode by an insulator and is contacted by source and drain electrodes. On
applying a negative gate bias Vg between source and gate, holes accumulate at the
interface between semiconductor and insulator. The increased charge carrier density
causes a highly conductive channel to open between the source and the drain contact. The
transistor is switched on and a current can be driven between source and drain once a
drain bias Vd is applied. By applying a Vg that does not allow for charge carrier
accumulation, the transistor can be switched off.
29
Organic Light-Emitting Field Effect Transistor
a, In the ambipolar regime of an OLET, the electrical fields at the source and drain
contacts allow for the accumulation of electrons and holes in the transistor channel. This
is illustrated by the comparison of the gate, source and drain potentials
for Vd exceeding Vg. b, The structure of the OLET used by Capelli and coworkers consists of a trilayer stack of semiconducting materials on top of the insulator
and gate layers where an emission layer is sandwiched between an electron30
transporting and a hole-transporting layer.
Ambipolar transport in donor/acceptor mixtures
31
A Light-Emitting Field-Effect Transistor
J. H. Schon et al., Science 290, 963 (2000)
Drain current of an ambipolar a-6T FET at room temperature as a function of positive drainsource Vd bias for different gate-source voltages Vg. At high gate voltage, the electron current
dominates, whereas hole conduction becomes noticable at low gate and high sourcedrain
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voltages.
A Light-Emitting Field-Effect Transistor
Color plot of the channel conductivity of an ambipolar a-6T FET as a function of gate-source
and drain-source bias on a logarithmic scale. The dashed line corresponds to more or less
balanced electron and hole currents (Vd 2Vg).
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Organic light-emitting transistors
A general schematic illustration for the
light-generation process of an ideal
single-component ambipolar OLET.
Typical paradigms for unipolar OLETs using interdigitated Au films
as hole-injecting and electron-injecting electrodes. A) Cross section of
the first OLET using tetracene as active layer. B) p -type output characteristics of
the OLET under different bias conditions. C) Optical image of the illuminated
channel of the as-constructed tetracene-based OLET, where typical green
emission close to the drain electrode could be observed. D) Schematic of the
tetracene-based OLET with the indication of the underetched source and drain
contacts, wherein the unipolar recombination at the drain electrode is
schematically illustrated. E) The image of the underetched contacts of the
34 PF2/6based unipolar OLET directly observed by SEM.
Major Contributors: IBM
IBM has used CNTs and their ambipolar characteristics to produce
nanotube light sources. One prototype used a 1.4-nm diameter
nanotube to produce light through the collision of holes and
electrons. Varying the gate voltage also controlled where along
the length of the CNT the light was emitted.
Nanotube Light
Varying the Light Emission Point
35
Carbon Nanotube Based Light-Emitting Transistors
Infrared emission from a carbon nanotube-FET during a gate voltage sweep (3D
plots where x and y are lateral directions on the device and z is the IR intensity.)
The light intensity is also color-coded. An image of the electrodes is superimposed
on all frames to help identify the emitting location. The nanotube (not visible) is
aligned vertically between source and drain.
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Polymer Light Emitting Field-Effect Transistor
Drain
(Ag)
Conjugated Polymer
+++++++
+++++++
-----------------
Source
(Ca)
Gate Dielectric
Gate
Qualitative description of device operation:
Gate controlled “p-n junction”
Light emission from the overlap recombination zone
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Controlling Emission Zone
Gate voltage controls the electron current,
the hole current, and the brightness!
| I ds|
[ A]
10
8
6
1E-8
4
PMT Current
12
1E-7
| a.u.|
14
2
1E-9
0
30
60
Vgs
90
120
0
150
[ V]
h
150 V
Au
h+ transport
dominates
ground
Ca
Vg < Vsd/2
Ambipolar
transport Vg  Vsd/2
dominates
e- transport
dominates Vg > Vsd/2
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Maximum Efficiency
Maximum efficiency at crossover point
where electron and hole currents are equal.
| I ds|
[ A]
10
8
6
1E-8
4
PMT Current
12
1E-7
| a.u.|
14
2
1E-9
0
30
60
Vgs
90
120
0
150
[ V]
h
Ambipolar
transport Vg  Vsd/2
dominates
39
Organic light-emitting transistors
OC1C10-PPV ambipolar light emitting field effect transistor employing Au and Ca contacts for
the hole and electron injecting electrodes: a) Movement of the emission zone as a function of the
applied bias: Vg = –90 V and Vds = –79, –86, –93, –100 V, from left to right. b) Transfer
40
characteristics at Vds = –80 V. c) Output characteristics.
41
42
43
Organic light-emitting transistors
44
Organic light-emitting transistors
45
Organic light-emitting transistors with an efficiency that
outperforms the equivalent light-emitting diodes
Trilayer OLET device structure and active materials forming the heterostructure. a,
Schematic representation of the trilayer OLET device with the chemical structure of each
material making up the device active region. The field-effect charge transport and the lightgeneration processes are also sketched. b, Energy-level diagram of the trilayer
heterostructure. The energy values of the HOMO and LUMO levels of each molecular
material are indicated together with the Fermi level of the gold contacts.
46
Organic light-emitting transistors with an efficiency that
outperforms the equivalent light-emitting diodes
Images of the light-emitting area within the OLET device channel. a, For reference, an
optical micrograph of the device channel without bias, to highlight the position of the drain
electrode edge that is marked with a yellow line. b–d, Optical micrographs of the emission
zone within the device channel of the trilayer heterostructure OLET during a transfer scan at VDS
=90V and VGS values of 30V (b), 60V (c) and 90V (d). Three arrows in b–d indicate the initial
47
position of the recombination and emission zone.
Organic light-emitting transistors
A facile protocol for the construction of unipolar OLETs with short channel length asymmetric contacts, wherein Al
and Au fi lms are successively deposited at angles of 60° and -60° on the opposite sides of the substrate.
Typical example for high-performance unipolar OLETs in
terms of multifunctional electrodes. A) A scheme of the
proposed bottom-contact device with Mg:Au (alloy of Mg
and Au)/Au multifunctional electrodes. B) A simulation
indicates a shift of the recombination zone from the
organic/insulator interface in the vertical direction toward
the electrode with increasing Vg.
48
Unipolar OLET of evidently enhanced performances by an
introduction of a conjugate polyelectrolyte
Unipolar OLET of evidently enhanced performances by an introduction of a conjugate polyelectrolyte
(CPE) layer atop the emissive layer to circumvent the electron injection barrier. A) A schematic device
architecture of the as-proposed OLET of a CPE layer. B) A model of electron injection from the drain
electrode modifi ed by the presence of an interfacial dipole layer. The emissive layer corresponds to SY. C)
Photographs of the light emission of the devices of RGB colors. The devices using MEH-PPV, SY and
PFO as emissive layers display orange (left), yellow-green (middle) and blue emissions (right),
49
respectively.
Organic light-emitting transistors with an efficiency that
Schematic illustrations of ambipolar LE-OFETs consisting of (a) single layer, (b) bulk heterojunction,
and (c) bilayer heterojunction LE-OFET structures.
A schematic illustration of the three typical geometries of heterojunction-based
ambipolar OLETs. A) Bulk heterojunction. B) Layered heterojunction. C) Laterally
arranged heterojunction.
50
High-performance ambipolar OLETs in terms of device
configuration
F8BT
Typical examples for high-performance ambipolar OLETs in terms of device configuration. A) The scheme of F8BT-based
ambipolar light-emission device of a bottom-contact/top-gate confi guration with Au electrodes and PMMA dielectric layer.
B) Optical images of the controlled emission zone of the as-formulated transistor during transfer scans at V ds = –100 V and
different Vg (between ca. –35 and –50 V). C) Optical micrographs (top) and intensity profiles (bottom) of the
perpendicularly- (left panel) and parallel- (right panel) aligned F8BT–based OLETs. D) A schematic illustration of an F8BTbased top gate/bottom contact OLET structure with integrated waveguide rib and DFB grating (top panel), and an
environmental SEM image of the as-fabricated Ta2O5 waveguide rib structure with an additional DFB grating aligned to the
T-shaped gold electrode pattern (bottom panel). The inset shows a close-up of the grating on top and next to the ridge.51
Qualified ambipolar OLET
Qualified ambipolar OLETs of controlled efficiency, brightness, and recombination
zone realized by means of using a split-gate architecture. A) A schematic illustration
of the as-proposed device of a split-gate. B–D) EL zone of the devices observed
under vairous bias conditions.
52
Device physics of single component-based ambipolar OLET
Device physics of single component-based ambipolar OLETs disclosed by means of using
different bias conditions, wherein three important emission regimes could be discerned. A) Vg
< Vds /2, hole transport dominates. B) Vg ≈ Vds/2, ambipolar transport dominates. C)
Vg > Vds/2, electron transport dominates. D) Confocal microscopy images of the emission
zone collected as it moved across the channel region of the device. Cross section plots of
emission intensity vs lateral position in each scan are shown on the right. Cursors and the
extended dotted lines depict the location of the electrode edges that define the channel region
53
qualified ambipolar OLET of high luminescence, high carrier
mobility, and edge emission
Typical example for qualified ambipolar OLET of high luminescence, high carrier mobility, and edge
emission, etc. achieved by using single crystal OSC. A) Edge emission observed from a BP3T singlecrystal-based OLET during ambipolar operation under ambient light conditions. Light emission points are
indicated by arrows. B) A schematic illustration for the as-proposed self-waveguided edge-emission. C)
Real-time drain current-dependent spectral evolution of the as-constructed devices during a Vd sweep,
wherein a spectral narrowing at a high current regime with brighter emission could be realized.
54
RGB emission from an individual OLET
An interesting example for the RGB emission from an individual OLET, which is realized by using an
ultrathin OSC single crystal as the active layer. A) The PL and absorption spectra of the DPVA thin single
crystal fi lm. The gray area shows the overlap between the two spectra. B) The relationship between the
molecular orientation and the crystal surface in DPVA, tetracene and AC5 single crystals. The ab plane is
parallel to surface of the thin crystal. The red, blue and green arrows indicate the calculated directions of the
transition dipole moments in DPVA, tetracene and AC5 molecules, respectively. C) A conceptual
representation of the novel color tuning with a thin DPVA single crystal.
55
Ambipolar OLETs of color-tunable emission
Ambipolar OLETs of color-tunable
emission obtained by taking the
advantages of a layered heterojunction
structure and the spatial control of the
recombination zone. A) EL spectra of
ditetracene (circle) and tetracene (square). B) EL
spectra, photographs of the recombination zone,
and transistor schemes of such ditetracene and
tetracene bilayer-based OLETs under different
bias conditions. C) A schematic illustration for
the implantation of a rubrene color conversion
layer, which covered the transistor channel only
partially, by a parallax technique. D) Schematics
of a color tunable OLET using a color
conversion layer in form of a rubrene wedge
(left). Continuous emission arrows mark the
actual EL, while dotted emission arrows indicate
possible mixed emission by change in xr. L is
the channel length, xr is the position of the
recombination zone, xw is the distance of the
rubrene wedge onset from the source, and dd is
the rubrene layer thickness at the drain.
Micrographs of the transistor channel of a neat
F8BT-based OLET (top right corner) and the
corresponding OLET with rubrene-based color
conversion layer (bottom right corner) under
56
operation.
Typical paradigms of OLETs of a vertical structure
Typical paradigms of OLETs of a vertical structure. A)
OSIT of a very short distance between the source, drain and
gate electrodes. In as-configured device, gate electrodes of a
pattened grid are inserted inside the hole transport layer, which
is sandwiched between the source (anode) and the emissive
layer with drain (cathode) electrodes position atop of the
emissive layer. B) A scheme for the construction of vertical
OLETs by integrating OFET and OLED directly into a single
stacked device, wherein RGB emission could be easily
realized.
57