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Beta-phase gallium oxide (β-Ga2O3) has attracted attention in recent years as a potentially low cost, large area substrate and active layer material for high power, high temperature power electronics and sensing devices. However, growth of β-Ga2O3 crystals is complicated by easily activated (100) and (001) cleavage planes, the presence of low angle grain boundaries (LAGBs) and twins, and the potential formation of polycrystalline grains. In this study, β-Ga2O3 crystals were grown by the edge-defined film-fed growth technique with an (010) principal face. Two crystals with apparently randomly formed high angle grain boundaries (HAGBs) were selected and analyzed by electron backscatter diffraction, electron channeling contrast imaging, and cathodoluminescence to investigate the nature of the LAGBs and the source of the HAGB formation. It was discovered that planar LAGBs lying parallel to the (010) plane exist in the region immediately preceding the start of an HAGB. Increased misorientation across the LAGB was observed, approaching the initiation of a new grain. We present multimodal microscopy characterization, correlating misorientation and variation in optoelectronic properties with LAGBs and the associated dislocations. [ABSTRACT FROM AUTHOR]

Photo-induced conductivity transient spectroscopy (PICTS) and cathodoluminescence (CL) measurements were performed on nominally undoped detector grade samples of TlBr. In PICTS measurements, nine traps were detected in the temperature range 80-250 K using four-gate analysis. Five of the traps are tentatively identified as electron traps, and four as hole traps. CL measurements yielded two broad peaks common to all samples and most likely associated with defects. Correlations between the optically and electrically detected deep levels are considered. Above 250 K, the photoconductivity transients measured in the PICTS experiments exhibited anomalous transient behavior, indicated by non-monotonic slope variations as a function of time. The origin of the transients is under further investigation, but their presence precludes the accurate determination of trap parameters in TlBr above 250 K with traditional PICTS analysis. Their discovery was made possible by the use of a PICTS system that records whole photoconductivity transients, as opposed to reduced and processed signals. [ABSTRACT FROM PUBLISHER]

Nonuniformity in charge transport properties is a limiting factor in energy resolution of radiation detectors. In this paper, we investigate variations in the low temperature ambipolar diffusion length and the mobility-lifetime (\mu \tau) product in bulk doped TlBr using cathodoluminescence (CL) and transport imaging. One TlBr crystal was doped with sodium (Na), aluminum (Al), and silver (Ag). A second TlBr crystal was doped with copper (Cu), iron (Fe), and zinc (Zn). We report the first low temperature high resolution CL spectroscopy and mapping in bulk doped TlBr, showing spatial variation in recombination luminescence on a scale of \sim 10~\mum. Transport imaging is applied to quantify these variations in TlBr at 5 K. Ambipolar diffusion lengths and \mu \tau products, dominated by the transport of holes, are mapped across a 40~\mum segment of TlBr at a resolution of 2~\mum. Ambipolar diffusion lengths are found to vary between 4.6~\mum and 11.2~\mum, on a spatial scale comparable to the variation observed in the CL map. [ABSTRACT FROM PUBLISHER]