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Temperature-dependent cathodoluminescence spectra were measured for rock salt-structured MgxZn1−xO films with x = 0.95–0.61. The Mg0.95Zn0.05O film exhibited the shortest deep UV peak wavelength of 199 nm (6.24 eV) at 6 K. Relatively high equivalent internal quantum efficiencies of 0.9%–11% were obtained. The Tauc plots, which were obtained from temperature-dependent optical transmittance measurements, exhibited large Stokes-like shifts of 0.7–0.9 eV at 6–300 K. Time-resolved photoluminescence (PL) signals at 7 K exhibited fast and slow decay components. The fast decay component had PL lifetimes of 2.59–3.08 ns, and the slow decay component far exceeded the measurement time range of 12.5 ns. The fast decay constant reflected the transfer lifetime of the photoexcited carriers to certain trapping centers. These centers were tentatively ascribed to Zn-related isoelectronic trapped-hole centers and may be a cause of the large Stokes-like shifts. The signals at 300 K exhibited very short PL lifetimes of 120–180 ps. The PL lifetimes were mainly attributed to the nonradiative recombination lifetime. Simultaneous decreases in the Zn-related isoelectronic trapped-hole centers and the nonradiative recombination centers were found to be necessary to improve the DUV emission properties of RS-MgxZn1−xO films. [ABSTRACT FROM AUTHOR]

We investigated bandgap engineering of spinel-structured Mg B 2O4 (B = Al, Ga, In) alloys. The trend of bandgap change was tunable from approximated 7.8–3.6 eV by substituting group III cation atoms in Mg B 2O4. To evaluate the doping possibility, we have calculated the natural band alignment and doping pinning energy of the normal and inverse spinel structures of Mg B 2O4 alloys. The calculated doping pinning energies show that spinel-structured Mg B 2O4 alloys can potentially control the electron concentration, but hole doping is difficult. Our computational results are expected to provide new insights into the doping control of ultra-wide bandgap semiconductors. [ABSTRACT FROM AUTHOR]

Routes to semi-stable phases of Ga 2 O 3 are the subject of extended discussions based on the review of growth methods, growth conditions, and precursors in works that report semi-stable phases other than the thermally stable β phase. The focus here is on mist chemical vapor deposition because it has produced single-phase Ga 2 O 3 of α , γ , and ε (or κ) in terms of the substrate materials, and features of this growth method for phase control are emphasized. Recent reports of phase control by other growth technology give a deeper understanding of how to determine and control the phases, increasing the opportunities to fully utilize the novel and unique properties of Ga 2 O 3. [ABSTRACT FROM AUTHOR]

We have calculated formation enthalpies, bandgaps, and natural band alignment for MgO1−xSx alloys by first-principles calculation based on density functional theory. The calculated formation enthalpies show that the MgO1−xSx alloys exhibit a large miscibility gap, and a metastable region was found to occur when the S content was below 18% or over 87%. The effect of S incorporation for bandgaps of MgO1−xSx alloys shows a large bowing parameter (b ≃ 13 eV) induced. The dependence of the band lineup of MgO1−xSx alloys on the S content by using two different methods and the change in the energy position of the valence band maximum (VBM) were larger than those of the conduction band minimum. Based on the calculated VBM positions, we predicted that MgO1−xSx with S content of 10%–18% can be surface charge transfer doped by high electron affinity materials. This work provides an example to design for p-type oxysulfide materials. [ABSTRACT FROM AUTHOR]

The epitaxial growth of α‐In2O3 films by mist chemical vapor deposition (mist CVD) using In2O3 powder as a source precursor is conducted. To prepare the source precursor solution, the In2O3 powder is first dissolved in HCl aqueous solution. The concentrations of HCl in the source precursor solution are then adjusted to be between 0.82 and 2.3 mol L−1 by adding deionized water. An enhancement in α‐In2O3 phase formation and increases in its grain size and thickness are observed with increasing HCl concentration. A pure α‐In2O3 film grown using a source precursor solution with 1.2 mol L−1 of HCl shows a residual electron concentration of 8.4 × 1017 cm−3 and electron Hall mobility of 216 cm2 V−1s−1. [ABSTRACT FROM AUTHOR]

Rocksalt‐structured (RS) MgZnO crystals are grown on quartz glass substrates by the mist chemical vapor deposition (mist CVD) method. Cathodoluminescence (CL) emission properties are comparatively studied with those for the RS‐MgZnO epitaxial film prepared on MgO substrate to explore their potential for vacuum ultraviolet (VUV) emitter. In the experiment, the newly developed VUV spectroscopy system is employed, where the CL and optical transmittance spectra are simultaneously measured. Growths of RS‐MgZnO on quartz glass substrate indicate formation of microcrystals (MCs). The MCs dominantly exhibit a near‐band‐edge VUV emission at 6.20 eV (200 nm) at 6 K and 6.07 eV (204 nm) at 300 K. Moreover, the MCs show a noticeable higher energy shoulder at 6.6 eV (188 nm) at 6 K and 6.4 eV (194 nm) at 300 K. The results ensure potential of RS‐MgZnO crystals for active element in VUV emitter regardless of the substrate material. [ABSTRACT FROM AUTHOR]