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This paper focuses on the detailed investigation of the structural and electronic properties of wurtzite AlN crystals doped by Li with and without oxygen with the first principles calculation. All the calculations have exhibited significant structural distortions. Compared with the monoclinic doping, the oxygen codoping has improved the structure deformation and lowered the formation energy of Li dopants. The calculated electronic density of states (DOS) reveals that all doping configurations still preserve semiconductor characteristics. The states around the valence band maximum cross the Fermi level, which implies p-type doping. The induced extra levels are extremely localized and flat in Li-doped AlN while much more delocalized in oxygen codoped models. The mono-doping of Li is in general energetically unfavorable while the codoping improves the formation and makes the intercalation of Li more stable in AlN. According to the results, the codoping configuration of Li with O in AlN has provided a useful way of modifying the corresponding properties. [ABSTRACT FROM AUTHOR]

Bandgap engineering offers opportunities for tailoring the properties of semiconductor materials for desired applications in microelectronics and optoelectronics. Alloys of different semiconductor materials can lead to the continuously tuning of the bandgap. Here, we report the bandgap engineering in layered InSe single crystals by substituting the Se atoms with S atoms. The formation of InSxSe1-x single crystal alloy with x ≤ 0.3 is evidenced by the X-ray diffraction and resonant Raman spectra. The photoluminescence (PL) spectra peak position blue shifts from ~1.27 to ~1.42 eV as S composition increases from 0 to 0.3 in the alloys, which is consistent with the bandgap shifts calculated by density functional theory. Temperature dependence of the PL spectra indicate that the presence of S atoms decreases the strength of the electron-phonon interaction but increases the average phonon energy in InSxSe1-x alloys. Our findings will open an intriguing avenue in understanding the fundamental physics in the III-VI layered semiconductor materials and their potential applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]