The spatial distributions of the cathodoluminescence (CL) emissions from thin ZnS films on GaAs(100) have been examined by the low-temperature CL measurement system combined with a transmission electron microscope (TEM). The correlation between these CL emissions and structural defects were studied by comparing the monochromatic CL images with the TEM images for both plan-view and cross-sectional observations. It is found that the neutral acceptor–bound exciton associated emission (A0,X) and the free-electron-to-ionized acceptor transition emission (e,A) are affected by the stacking fault distribution. The localization of the emission due to the deep-level emission transition near the interface suggest the diffusion of Ga atoms from the GaAs substrate. The characteristic distributions of the CL emission regions can be explained by considering the competitions among the recombination channels of those radiative processes for each type of an excess carrier, an electron, or a hole.

This work reports growth of α-(AlxGa1-x)2O3 single crystals with high incorporation of Al by a Mist Chemical Vapor Deposition two-chamber system, which was rationally designed to avoid side-reactions between different precursors during solution preparation for multi-component thin film growth. Multiple acceleration voltages were used in Energy Dispersive X-ray measurements to reliably obtain the Al composition x of the films. As a result, Vegard's law for lattice constants was verified and found to be valid in the α-(AlxGa1-x)2O3 system. However, Vegard's law for optical bandgaps, derived from different models, required an additional term to account for the bowing effect. At x = 0.71, the gaps were 7.74, 7.03, 7.26, and 7.34 eV as derived from the Tauc plots for the direct bandgap, indirect bandgap, Tauc-Lorentz model, and O'Leary-Johnson-Lim model, respectively. The two-chamber system provides reliable and effective control of the Al content in α-(AlxGa1-x)2O3 alloys and heterostructures.

We measured the reliability of two different organic light-emitting diodes (OLEDs) composed of indium tin oxide (ITO)/4,4 0bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (-NPD)/tris(8-hydroxyquinoline)aluminum (Alq 3 )/MgAg (two layer) or ITO/ -NPD/-NPD:Alq 3 (mixed layer)/Alq 3 /MgAg. Changes in the carrier trap distribution were estimated by thermally stimulated current (TSC) measurements. Improved device reliability was observed in the mixed-layer device. In the case of the twolayer device, the TSC peaks gradually changed depending on the duration of continuous operation, while the mixed device showed no change in its TSC spectra. These spectral differences indicate that the mixing of -NPD and Alq 3 occurs during the continuous operation in the two-layer device.

No abstract

No abstract