topics acophys “opening week” get-together by examples 1.) organic optoelectronics 2.)...
DESCRIPTION
Semiconductors : An energy gap separates states of mobile electrons from states of mobile holes in the so-called valence band, which is otherwise occupied by electrons. What happens if electrons and holes meet ? What happens at the interface of two semiconductors ? Energy PositionTRANSCRIPT
Topics ACOPhys “Opening Week”
Get-together by examples
1.) Organic Optoelectronics2.) Electronic Structure of Organic Materials3.) Plastic Solar Cell4.) Random Matrix Theory and Excitons in Disordered Quantum Wells
Planning next steps
Get-together by means of examples:
Discussing Quantum Wells and Wires
Prof. Gerhard Gobsch, “Applied Physics”Prof. Erich Runge, “Computational Physics”Technical University of Ilmenau, Institute of Physics
Semiconductors: An energy gap separates states of mobile electrons from states of mobile holes in the so-called valence band, which is otherwise occupied by electrons.
What happens if electrons and holes meet ?
What happens at the interface of two semiconductors ?
Ene
rgy
Position
Light Emitting Diodes (LED) + Semiconductor quantum well lasers
... and the hairy details as presented by the world‘s best-known expert
The simple view of a theoretical physicist...
Ene
rgy
Position
Nobel prize 2000: Kroemer und Alferov
http://britneyspears.ac/physics/fplasers/images/dhlaser.jpg
Light Emitting Diodes (LED) + Semiconductor quantum well lasers
... and the hairy details as presented by the world‘s best-known expert
The Gallium Nitride Revolution: LEDs and lasers based on InGaN / GaN quantum wells
Does the revolution eat its children? ‘‘Long reign the OLED’’
1.0
00
2.0
3.0
4.0
5.0
6.0
7.0
350300
400500600800
AlN
GaN
InN
InGaN
infra-red
visible
ultra-violet
0.2 0.4 0.6 0.8 1.0x
AlGaN 250
200
band
gap
(eV
)
wav
elen
gth
(nm
)
Band gaps of hexagonal nitride compounds
What about Quantum Mechanics ?
http://www.almaden.ibm.com/almaden/media/image_mirage.html
Electrons show wave-like properties, ...
... some of them are easily explained ...
... and some are a bit harder to get used to ...
Ener
gyPosition
What about Quantum Mechanics ?
0 1 eV 2 eV 3 eV 4 eV
Infra red Ultraviolet
CdSe nano spheres covered with ZnSe act as quantum dots
http://www.evidenttech.com/products/core_shell_evidots/overview.php
2 nm
: Lak
e Pl
acid
Blu
e
5 nm
: Map
le-R
ed O
rang
e
confh
2m LE
2~~
2
2
Confinement energy ... some of them are easily explained ...
ExcitonsEnhanced particle-particle interaction: e-h bound state
... some of them are easily explained ...
100 meV
2-20 nm
1.5 eV
EB =5 meV
Computation of quantum wire excitons
Disorder-free structures,exciton parameters Dispersion of multi-subband QWR excitons low-energy states of 107 X 107 matrix electron-hole correlation decomposition into valence-band orbitals dispersion relation and exciton mass MX
spin-splitting, polarization anisotropy
A. Siarkos, E. Runge, PRB 61, 16854 (2000)
Spatially resolved spectroscopyK. Matsuda et al., PRL 91, 177401 (2003): 30 nm resolution, wavefunction mapping
but: Ch. Lienau, E. Runge, Physik Journal, Jan. 2004 and to be published