Absorption and reflection spectra of β-Ga2O3 are measured with polarized light in the wavelength region near its absorption edge. The crystals of β-Ga2O3 are grown by using a Ga/HCl/O2/Ar vapor reaction system. The platelike crystals of β-Ga2O3 have (100), (010), and (001) surfaces, and the major surface is (100). The energies of the absorption edge are observed to be 4.90 eV for E//b, 4.54 eV for E//c, and 4.56 eV for E⊥b&c at room temperature. The energies for E//b and for E//c at 77 K are larger than those at room temperature by 40 meV and 220 meV, respectively. Reflection minima are observed at 5.06 eV and 5.30 eV for E//b, and at 4.63 eV and 5.30 eV for E//c at room temperature.

The photoluminescence and optical absorption properties of Zn-doped GaS crystals prepared by the iodine vapor transport method are reported. Undoped GaS crystals are also used for comparison. Zn substituted for a Ga site acts as an acceptor having a deep energy level and forms a complex with the iodine coactivator, which can be the luminescence center. When increasing the charged amount of Zn, the near-blue emission band of 2.47 eV at 97 K becomes dominant, while the 2.17-eV emission band due to the Ga vacancies, which is dominant in the undoped crystals, gradually vanishes because of the reduction of the Ga vacancies. It is thus described that Zn is a promising dopant in GaS for near-blue-light-emitting devices.

No abstract

No abstract

In this work, we propose a new non-Abelian generalization of the Born-Infeld Lagrangian. It is based on a geometrical property of the Abelian Born-Infeld Lagrangian in its determinantal form. Our goal is to extend the Abelian secondtype Born-Infeld action to the non-Abelian form preserving this geometrical property, which permits us to compute the generalized volume element as a linear combination of the components of metric and the Yang-Mills energymomentum tensors. Under the BPS-like condition, the action proposed reduces to that of the Yang-Mills theory, independently of the gauge group. New instanton-wormhole solution and static and spherically symmetric solution in curved spacetime for an SU (2) isotopic ansatz are solved and the N = 1 supersymmetric extension of the model is performed.PACS numbers: 11.25.Hf, 12.60.JvRecently, interest has increased in this nonlinear electromagnetic theory since it turned out to play an important role in the development of string theory, as was very well described in the pioneering work of Barbashov and Chernikov [5]. The nonlinear electrodynamics of the Born-Infeld Lagrangian, shown in [24], describes the low-energy process on D-branes