### 金属・量子井戸ヘテロ界面における動的共鳴現象 - 半導体における動的

```金属・量子井戸ヘテロ界面における動的共鳴現象

を解明する。本講演では、量子井戸内に生成される励起子エネルギーのヘテロ界面における金属層の帆表面自由

Structure of 4.8 nm-thick SQW and PL quenching
Critical temperature (Tc) for PL quenching effect
Coupling of excitons and surface free electron oscillation
0
-4 Difference PL
DI / I = 1000%
-8
1.8
3
T = 300 K
100K
60K
2.2
2.6
20K
2.2
SQW emission peak energy (eV)
PL quenching ratio (time)
0
-4
Tc = 125 K
-8
-12
0
Tc = 90 K
-4
-12
3.02
LW = 2.3 nm
3.005
10
100
Ag layer
Photon-counting
2.93
LW = 3.2 nm
2.9
Ti: sapphire
E(0) = 2.965 eV
s = 20 meV
2.87
2.79
LW = 4.8 nm
E(0) = 2.808 eV
s = 8.5 meV
0
100
200
Without Ag
With Ag
10 K
t1 = 0.266 ns
t2 = 2.09 ns
t1 = 0.242 ns
t2 = 1.75 ns
75 K
t1 = 0.148 ns
t2 = 0.771 ns
t1 = 0.136 ns
t2 = 0.686 ns
300
Temperature (K)
Temperature (K)
SQW
6.2 nm
2.77
2.73
300
I (300K )
= 2.0%
I (8K )
Integrated PL intensity (a.u.)
tNR
t PL =
I1t 1 + I 2t 2
I1 + I 2
~
T1.5
1
40
80
1000 / T (K-1)
120
+
t
PL
1
tR
+
tET metal t2
t1
1
t ET -metal
1
hinteq =
t NR
T = 10 K
tPL
0.1 10
=
=
1
C.B.
100
1+
tR
t NR
I(t) = I1*exp(-t/t1) + I2*exp(-t/t2)
Without Ag
With Ag
T = 10 K
T = 75 K
0
1
2
Time (ns)
tNR
Energy Transfer was induced by longer lifetime
(t2) than energy transfer lifetime (t ET metal).
Ag metal nanodots by EB lithography for nano-optics
0.5
Without Ag
With Ag
0.3
0.1
10
T = 100 K
× t1
V.B.
Temperature (K)
1
×
tNR
InGaN laser: 403 nm
0
t PL ,metal
tR
1
300
1
t PL
hinteff =
100
200
Temperature (K)
Energy transfer from quantum well to metal
Radiative recombination process in SQW without Ag region
DE = 10. 5 meV
0
Long lifetime (t2): localized states in the SQW
Integrated PL intensity and effective PL lifetime
10
2.73
Selective excitation of the well (2.8 eV)
2.75
-8
3
Difference of lifetime between without and with Ag regions
E(0) = 3.093 eV
s = 29 meV
3.035
2.6
Photon energy (eV)
s = 8.5 meV
Ti: sapphire second harmonic laser (l = 408 nm)
Laser pulse width: 2 ps
Photo-counting system (resolution: 80 ps)
0
-12
2.75
Time-resolved PL response of 4.8 nm-thick SQW
Excitonic localization and quenching temperature
Tc = 140 K
a 2T
s2
T +b
k BT
Correlation of quenching temperature and localization of excitons
Quantum well size and PL quenching effect
-8
E (T ) = E ( 0 ) -
3
Photon energy (eV)
-4
-8
2.77
30K
1.8
DI / I = 0%
1.8
Tc ~ 90 K
-12
10K
0
-4
-8
-4
2.79
40K
SQW
direction
2.6
200K
150K
PL intensity (a.u.)
Difference
Exciton (e- -h+ pair)
vibrating dipole
2.2
Photon energy (eV)
0
SQW energy (eV)
With Ag layer
PL intensity (a.u.)
Electromagnetic field
Space (t)
0
Without Ag layer
(SQW surface roughness : 1-1.5 nm)
Ag (silver) metal
300K
T = 10 K
Difference PL intensity (a.u.)
Difference
ZnO Spacer
CdZnO well
ZnO Buffer
Quantum confinement of excitons and the Quenching appearance
PL quenching ratio
PL intensity (a.u.)
t = 4 nm ZnO spacer thickness
1
t ET metal
~ 1 ns
0.1 10
100
Temperature (K)
Conclusion
1. PL quenching effect was observed at low temperatures and
was related to a quantum confinement size.
2. PL quenching was ascribed with a decrease of lifetime, and