Fig. 1. Wave functions of the ground electron and hole states in different quantum wells at bias Ub=3.4V.
The spectrum of light emission from a single- or multiple-quantum-well
active region is calculated with account of the complex valence band
structure of wurtzite semiconductors by using the 8×8 Kane Hamiltonian.
Energies and wave functions of localized carrier states are found from
numeric solution of the Schrodinger equation within the effective-mass
approximation. Generation of the grid for each QW is totally automatized in
the SiLENSe code.
Fig. 2. Electric current versus bias for the MQW LED (comparison with experiment).
- Exact account of localized and distributed polarization charges in the LED structure induced by both spontaneous and piezo polarization in nitride semiconductors;
- Fermi statistics is used for electrons and holes covering the cases of both degenerate and non-degenerate semiconductors;
- Partial ionization of donors and acceptors depending on the respective quasi-Fermi level positions is allowed for;
- Strain in the LED structure is calculated assuming coherent growth of all epilayers on an underlying buffer layer, the user can specify partial strain relaxation in some layers;
- Bimolecular radiative electron and hole recombination is considered with neglect of quantum-confined effects on the recombination rate;
- Non-radiative carrier recombination on threading dislocation cores, point defects, and Auger recombination. We have developed an original model of non-radiative recombination on dislocation cores with account of IQE increase due to carrier localization on fluctuations of In composition;
- I-V characteristic of an LED is computed with a given serial resistance that should account for both the lateral current spreading in the LED chip and ohmic contact resistances;
- Fig. 3. Light emission efficiency versus current density. Data on the external emission efficiency are plotted by circles. Effect of dislocation density on the internal emission efficiency is shown.
- Distribution of the electric/magnetic field in TE/TM waveguide modes is computed with account of birefringence of III-nitrides. An original approximation of the frequency-dependent dielectric constant of III-nitride covers the whole spectrum range*;
- Optical loss because of free carrier absorption is obtained from the known distribution of the electric field intensity in the mode and the carrier concentration*.