Optical characteristics of deep ultraviolet light-emitting diodes with the consideration of spontaneous and piezoelectric
polarizations are studied in this article with the APSYS (Advanced Physical Model of Semiconductor Devices)
simulation program. The amounts of surface charges caused by different polarizations are calculated and compared.
Moreover, the band diagram, carrier distribution, radiative recombination current, and light-current performance curves
of the InAlGaN UV LED structures with different polarizations are also discussed and investigated. According to the
simulated results, we find that the influence of the spontaneous polarization is more apparent than the piezoelectric
polarization on band properties, carrier distribution, radiative recombination and output power in deep UV spectral
region. In other words, for nitride materials in deep UV region, the polarization resulted from lattice-mismatch is smaller
than that caused by asymmetry of the structure along the c-axis. This conclusion is quite different from the situation of
blue InGaN light-emitting diodes. For blue LEDs, the piezoelectric polarization is the dominant polarization mechanism
because the lattice mismatch between compound layers is a severe problem for these long-wavelength LED devices.