Bandgap narrowing

FIGURE 5 shows the emission spectra of the UV LEDs at currents from 0.3 mA to 30 mA [3], With increasing forward currents, a redshift of the peak wavelength was observed, probably due to the bandgap narrowing caused by the heat generation at the junction. The blue shift due to the band-filling effects is minimised in this structure because the In composition is almost zero. 

Fig. 16.26 Various schemes of band structure change of (a) Pure anatase Ti02 (b) Doped-Ti02 with localized dopant levels near the CB and VB edges (c) Bandgap narrowing due to VB broadening (d) Localized dopant levels and electronic transitions to the CB (e) Electronic transitions of dopant levels near the VB edge to corresponding excited states for Ti3+ and F+ centers [Reprinted with permission from Serpone (2006). Copyright (2006) American Chemical Society]...

Umebayashi T, Yamaki T, Itoh H et al (2002) Bandgap narrowing of titanium dioxide by snUtir doping. Appl Phys Lett 81 454—456... 

In order to obtain a narrower bandgap of these oxides, the substitutional doping of N might be effective since its p states contribute to the bandgap narrowing by mixing with O 2p states [70]. The density functional theory calculations show that the valence band is composed mainly of the anion 2p orbitals hybridized with metal d states. In case of TaON, the upper energy level of the valence band is dominated by N 2p states [71]. 

The calculation was performed by direct numerical integration of (1.21) and using (1.27). The calculation did not take into account bandgap narrowing due to... 

Bandgap narrowing due to Coulomb interaction electron-electron may be written as [52]... 

Take La-C co-doping as an example, La and C substitutes Na and O, respectively, which nullifies the dopant-induced charge imbalance. Mid-gap states that spread over 1.5 eV can be formed due to the introduction of La and C, corresponding to the bandgap narrowing. 

H. P. D. Lanyon, R. A. Tuft, Bandgap Narrowing in Heavily Doped Silicon, p. 316, IEEE Tech. Dig., Int. Electron. Device Meet., 1978. 

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