SELES 1.0 — Segregation Effect on Light Emission Spectrum
1. Physical model
Calculated composition profile in MQW structure
The SELES software is specially designed for calculation of
characteristics of a LED heterostructure with account for surface segregation
effects. You can download SELES documentation, demo version, and
The main goal of the one-dimensional SELES code is to make a bridge from
MOVPE growth recipes to the characteristics of light-emitting diodes (LEDs)
based on a group-III nitride heterostructures. Basically, the LED
heterostructure consists of the n- and p-emitters, separated by a single or
multiple quantum well active region. But the real composition profile can be
significantly different from the "ideal" one, i.e. expected from the
precursor switching schedules and thick layers growth results.
Band diagram and wave functions of electron and hole ground
The indium surface segregation is
known to be the most important effect leading to such difference. The
segregation is known to be a factor affecting the composition profile in
the ternary and quaternary compound heterostructures with very different
volatility of the atomic species. Normally, segregation results in a
delayed incorporation of a volatile species into the crystal, in appearance
of the ternary compound tail in a binary "cap" layer, and, eventually, in
formation of liquid droplets. The strain in the epilayer due to lattice
mismatch is found to be a major factor affecting segregation.
The role of segregation in
limitation of In incorporation into the solid can be analyzed with the
software. With the SELES software, one can also estimate the effect of
composition profile variation on the LED characteristics. The known
composition profile is used to calculate the band diagram of the LED
heterostructure and light emission spectrum. An accurate quantum-mechanical
description of the carriers in the heterostructure, based on the
self-consistent solution of the Poisson and Schrodinger equations, is
provided within the SELES code.
The electroluminescence (EL) spectra computed with the package show that In
surface segregation normally results in a systematic blue shift of the EL
spectra (~50-100 meV) due to incomplete In incorporation into the crystal in
unsteady MOVPE growth . The bias variation produces the transformation of
the QW band diagram in such a way as new electron and hole states are formed
at high biases. The latter phenomenon results in a multi-peak structure of the
EL spectra and, consequently, in additional blue-shift of the emission
wavelength. Besides, the secondary peaks provide a higher broadening of the
spectra, which is undesirable for practical applications.
2. Capabilities of SELES 1.0
Distribution of indium content across an GaN/InGaN/AlGaN quantum well
The SELES 1.0 software includes the
- Calculation of the composition profile in a LED
heterostructure with account for indium surface segregation.
- Calculation of the band diagram of a LED heterostructure
at a given bias.
- Calculation of light emission spectrum at given bias.
3. User interface
The user interface includes
easy stage-by-stage input of the growth process in terms of real MOVPE
reactor: temperature, pressure, and precursor and carrier gas flow rates,
as well as visualization of the simulation results.
4. System requirements
User Interface. Input of growth regime
- Operation System—Windows 98/2000/ME/XP
- RAM—256 Mb
- Disk Space—2 Mb for the SELES program files
and about 1Mb per typical simulation to save results.
- Display and video card with the
support of 1024x768 resolution in the High Color
 Surface Segregation and Composition Fluctuations in
ammonia MBE and MOVPE of InGaN. S.Yu.Karpov, R.A.Talalaev, E.V.Yakovlev
and Yu.N.Makarov. Mat.Res.Soc.Proc., Vol.639, p.G3.18.2-G3.18.6, (2001).
 Indium segregation kinetics in MOVPE of InGaN-based
heterostructures. S.Yu. Karpov, R.A. Talalaev, I.Yu. Evstratov, and Yu.N.
Makarov. Physica Status Solidi (a), Vol.192, N 2, p.417-423, (2002).
 Indium segregation in MOVPE grown InGaN based
heterostructures. R.A. Talalaev, S.Yu. Karpov, I.Yu. Evstratov, Yu.N.
Makarov. Physica Status Solidi (c), Vol.01, p.311-314 , (2002).
 Segregation effects and bandgap engineering in InGaN
quantum-well heterostructures. K.A. Bulashevich, R.A. Talalaev, S.Yu.
Karpov, I.Yu. Evstratov, and Y.N. Makarov. Materials Research Society
Symposium Proceedings, Vol.743, p.L6.5.1-L6.5.6, (2003).