Numerical study of the current spreading and light extraction in deep UV light emitting diode
Date Issued
2015
Date
2015
Author(s)
Chen, Xinhui
Abstract
UVLEDs are in strong demands in recent years because of their special applications in industry and medicine. However, comparing with the commercial InGaN LEDs, the overall efficiency in UVLEDs is extremely low especially in UVC spectrum. The main reasons are found to be: (a) High defect densities in the AlGaN layer that result in low IQE; (b) The activation energy of Mg doped p-AlGaN layer is relatively high, which results in the poor hole injection and the increase of resistance; (c) Large absorption rate of the conventional p-GaN contact, which makes the light extraction efficiency much lower. To improve these issues, we focus on improving the current spreading and light extraction by considering different structures or different contact layers with Poisson and drift-diffusion solver to see how they influence the efficiency in UVLEDs. Moreover, we modeled a series of AlGaN superlattice structures to confirm that such a structure has a great potential of being used as the p-contact layer instead of p-GaN contact in UVLEDs. Finally, we discuss about the AlGaN UVB LEDs to find what the more important factor to limit their efficiency is.
Subjects
Ultraviolet light-emitting-diode
AlGaN
Current spreading
Light extraction
Superlattice
Type
thesis
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