Heterogeneous integration of β-(SnxGa1-x)2O3 (TGO) UV-C photodetectors on silicon substrates by molecular beam epitaxy is demonstrated. Multimodal electron microscopy and spectroscopy techniques reveal a direct correlation between structural, compositional and optical properties of the TGO and the functional properties of the photodetectors. Wavelength dispersive X-ray spectroscopy results accurately determine the Sn concentrations (x) in the region of 0.020, and room temperature cathodoluminescence (CL) hyperspectral imaging shows changes in CL emission intensity in the TGO compared with a Ga2O3 sample with no Sn. Alloying Ga2O3 with Sn is shown to quench the red emission and enhance the blue emission. The increase in blue emission corresponds to the rise in VGa-related deep acceptors responsible for the high gain observed in the TGO detectors. A Ga2O3 nucleation layer is shown to improve the TGO surface quality and give better device properties compared to TGO grown directly onto the Si substrate, including a higher specific detectivity on the order of 10 12 Jones. Introduction:The UV spectrum covers a wide range of wavelengths spanning 10-400 nm. The earth's atmosphere and ozone absorb UV-C (100-280 nm), removing radiation with wavelengths shorter than 280 nm from the solar spectrum that reaches its surface. Therefore, a detector designed to be sensitive to only these wavelengths is not affected by solar radiation and is said #

In this work, the growth and conductivity of semipolar AlxGa1-xN:Si with (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) orientation is investigated. AlxGa1-xN:Si (x = 0.60 ± 0.03 and x = 0.80 ± 0.02) layers were grown with different SiH4 partial pressures and the electrical properties were determined using Hall measurements at room temperature. The aluminum mole fraction was measured by wavelength dispersive X-ray spectroscopy and X-ray diffraction and the Si-concentration was measured by wavelength dispersive X-ray spectroscopy and secondary ion mass spectroscopy. Layer resistivities as low as 0.024 Ω cm for x = 0.6 and 0.042 Ω cm for x = 0.8 were achieved. For both aluminum mole fractions the resistivity exhibits a minimum with increasing Si concentration which can be explained by compensation due to formation of cation vacancy complexes at high doping levels. The onset of self-compensation occurs at larger estimated Si concentrations for larger Al contents.

We report ultra-high responsivity of epitaxial (Sn x Ga 1−x ) 2 O 3 (TGO) Schottky UV-C photodetectors and experimentally identified the source of gain as deep-level defects, supported by first principle calculations. Epitaxial TGO films were grown by plasma-assisted molecular beam epitaxy (PAMBE) on (-201) oriented n-type β -Ga 2 O 3 substrates. Fabricated vertical Schottky devices exhibited peak responsivities as high as 3.5×10 4 A/W at -5 V applied bias under 250 nm illumination with sharp cut-off shorter than 280 nm and fast rise/fall time in milliseconds order. Hyperspectral imaging (HSI) cathodoluminescence (CL) spectra were examined to find the mid-bandgap defects, the source of this high gain. Irrespective of different tin mole fractions the TGO epilayer exhibited extra CL peaks at the green band (∼2.20 eV) not seen in β -Ga 2 O 3 along with enhancement of the blue emission-band (∼2.64 eV) and suppression of the UV emissionband. Based on hybrid functional calculations of the optical emission expected for defects involving Sn in β -Ga 2 O 3 , V Ga -Sn complexes are proposed as potential defect origins of the observed green and blue emission-bands. Such complexes behave as acceptors that can efficiently trap photogenerated holes and are predicted to be predominantly responsible for the ultra-high photoconductive gain in the Sn-alloyed Ga 2 O 3 devices by means of thermionic emission and electron tunneling. Regenerating the V Ga -Sn defect complexes by optimizing the growth techniques, we have demonstrated a planar Schottky UV-C photodetector of the highest peak responsivity.

A high figure‐of‐merit UV‐C solar‐blind photodetector (PD) fabricated from thin‐film beta‐gallium oxide (β‐Ga2O3) grown on n‐Si substrates by plasma‐assisted molecular beam epitaxy is demonstrated. Film growth sequences for nucleation of Ga2O3 on (100)‐ and (111)‐oriented Si substrates are developed, and the influence of crucial growth parameters is systematically investigated, namely, substrate temperature, oxygen flow rate, and plasma power on the functional properties of the PDs. The PDs show an ultra‐high responsivity of 837 A W−1 and a fast ON/OFF time below 4 ms at −5 V. In addition, they display strong rectifying properties and a sharp cutoff below 280 nm with the average responsivities between 10 and 80 A W−1, a detectivity on the order of 1010 Jones, and rise/fall times between 4 and 500 ms. High photoconductive gain is likely to be due to the mid‐bandgap donor/acceptor defect levels, including oxygen vacancies in the form of self‐trapped holes. It is demonstrated that these defect levels can be modified by controlling the growth conditions, thereby allowing for tailoring of the PD characteristics for specific applications. The methodology represents a cost‐effective solution over homoepitaxial approaches, with characteristics that meet or exceed those reported previously, offering new possibilities for on‐wafer integration with Si opto‐electronics.

BACKGROUND: Work-related musculoskeletal disorders (WMSDs) remain a major occupational health problem, despite decades of research, outreach, and intervention. OBJECTIVE: The aim of this study is to promote early identification and prevention of WMSDs by developing education and outreach materials grounded in interview data collected from workers that have recently filed for workers compensation (WC) for WMSDs. PROCEDURES: We conducted semi-structured telephone interviews with WC claimants (n = 66) from high risk industries identified through the use of a Prevention Index (PI) in Washington state with WMSDs of the back, shoulder, hand/wrist, or knee. RESULTS: Perceptions regarding the degree of exposure to WMSD risk factors, the social construction of pain, and the potential to implement injury-prevention measures varied widely. Many workers dismissed their injuries as the result of "fluke" or "freak" occurrences and framed their exposure to risk factors for WMSDs as either inevitable or "just part of the job." CONCLUSIONS: Workers in high-risk industries for WMSDs described their work conditions in ways that suggested: (1) a lack of awareness of the potential for developing a WMSD, (2) a view of work-related pain as normal, and/or (3) a pattern of self-blame for WMSD onset. A paradigm that either asserts the inevitability of WMSDs or dismisses potential control measures presents both a significant barrier to injury prevention efforts as well as a major opportunity for future occupational health research.