Influences and control techniques of polarization charges generated in AlGaN heterostructure are described. Firstly the polarization charge density and its influences to carrier density and potential profiles were theoretically investigated. The density, 1×10^<13>cm^<-2>, typically generated in an Al_<0.2>Ga_<0.8>N/GaN interface resulted in a few 100 meV potential barrier. Secondly as an example showing adverse effects of the large potential barrier on device performances, a p-AlGaN electron blocking layer in a LED was described. A technique to suppress the adverse effects, diluting the polarization charges with graded layer, was then mentioned. Finally a new layer structure of a deep UV-LED accelerating the use of the polarization charges even in the case of the Al-face epitaxial growth was proposed. Such large polarization charge densities should be widely recognized, and the polarization charge engineering must be established along with the bandgap engineering.
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