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Conduction band profile and electron distribution for undoped (a) and 5 × 1021 cm−3 Si-doped (b) Al0.5Ga0.5 N/GaN superlattices. The electron wave function is superimposed on its bound state. Wells are depleted in undoped SLs, the nth bound states in each well are not coincident and no subband is formed. Obvious subbands are observed in (b). Electric field distributions for the corresponding undoped (c) and doped (d) SLs are presented. Comparison between them indicates that the electric field in the AlGaN barrier is restrained by doping.
Variation of electric field with increase in Si doping in GaN wells is presented in (a). The decrease in the electric field, as the doping concentration increases from 5 × 1017 to 5 × 1018 cm−3, is obviously not identical for each barrier. The conduction band profile and electron wave function for 5 × 1021 cm−3 doping is presented in (b). Arrows indicate the relationship between the electric field distribution in the GaN wells and the electron distribution in E1. (c) shows that the wells are occupied by electrons in sequence from the buffer/SL interface to the surface as the doping concentration increases from 2 × 1019 to 3 × 1021 cm−3.
Variation of E1-E0 with the increase in Si doping in GaN wells. E1-E0 decreases rapidly as the doping concentration increases from 2 × 1019 to 1 × 1020 cm−3. After that, the decreasing trend approaches saturation.
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