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Polarization-sensitive detectors are of great importance in the fields of remote sensing and imaging, environmental monitoring, and medical diagnosis. The surface plasmon effect can the enable polarization sensitivity of photodetectors through metallic gratings. However, limited by the precision of the nano-fabrication process, it is difficult to fabricate an ultraviolet (UV) polarization-sensitive detector integrated with sub-wavelength metal gratings and the polarization extinction ratio is relatively low. In this paper, an Al–ZnO composite double-layer grating structure was designed. The ZnO active layer and the Al layer were both fabricated into same-sized grating structures. Through this design, the slit width could be enlarged to some degree, while the response to 90° polarized light remained low. It is beneficial to realize a high polarization ratio and to spare the need for rigid fabrication accuracy. In addition, the influence of the structural parameters of the grating on the performance of the detector was studied by simulation. It was found that the resonance wavelength can be adjusted by changing the slit width and grating height, respectively. This provides a useful means for polarization-sensitive detection in different wavelength ranges. The polarization extinction ratio of the detector with a double-layer composite grating can reach 52 in the UV band (365 nm). This provides a good alternative to replace the traditional framework relying on the combination of polarizers and detectors. Moreover, it is a promising structure for high-density integrated photodetectors and imaging chips in the future. [ABSTRACT FROM AUTHOR]

This work demonstrates a ZnO single-crystal bulk-acoustic-wave (BAW) nuclear radiation detector based on piezoelectricity–photoconductivity interactions, which is suitable for developing a frequency-domain multiplexing system for cosmic X-ray and ${\gamma } $ -ray observations. The nuclear radiation-generated photocarriers in ZnO crystals screen the piezoelectric charge and reduce the acoustic velocity, inducing a negative resonant frequency shift for the detector. (0001)-oriented ZnO single crystals are used to fabricate high-quality BAW detectors. Unannealed and annealed crystal detectors are compared, and the annealed detector is found to show a higher signal-to-noise ratio and faster response speed due to a higher quality factor and fewer defects. The annealed ZnO crystal shows a resistivity of $10^{11} {\Omega } \cdot $ cm, a high electromechanical coupling factor of 10.4%, and a high quality factor of ~500. The annealed detector also shows a linear X-ray response with a responsivity of 0.89 k/Gy for an X-ray tube voltage of 70 kV, indicating great potential for application of bulk single-crystal-based BAW detectors in the field of nuclear radiation detection. [ABSTRACT FROM AUTHOR]

Semiconductor x-ray detectors are usually fabricated with proper ohmic or Schottky contact electrodes, which make the fabrication process complex and even unable to realize, especially for new materials. In this paper, we demonstrated an electrodeless ZnO single crystal x-ray detector using microwave (MW) bias with a high signal-to-noise ratio obtained by a cancellation method. The MW-biased x-ray detector is fabricated using the split-ring-resonator with the ZnO crystal mounted on the split-ring gap. The analytical response model was built for the detector. The MW cancellation process was realized by a phase and amplitude matching network. By using the cancellation method, the signal-to-noise ratio of the detector is about 59.4 dB, which is 58 dB higher than that of the DC-biased ZnO photodetector. The sensitivity of the detector is 139 µC Gy−1 cm−2 for the x-ray dose rate of 3.54 Gy/s, which is 86 times higher than that of the DC-biased ZnO photodetector. The high sensitivity of the detector is due to the high equivalent stimulated voltage caused by the split-ring resonator. The MW-biased detector can be used for x-ray dose monitoring. [ABSTRACT FROM AUTHOR]

A two-terminal 4H-SiC n-p-n bipolar phototransistor detector (PTD) with high gain is demonstrated. It was fabricated using the 4H-SiC epitaxial wafer grown by high-temperature chemical vapor deposition. The PTD shows a large photocurrent and responsivity enhancement over the conventional 4H-SiC p-i-n photodetector (PD). These enhancement effects are owing to the internal gain of the bipolar transistor. The detector shows a high optical gain of ~ 1450 at 360 nm and has a linear response to the ultraviolet (UV) light in the wide light intensity range of 0.7– 700 μW/cm2 at a low operating voltage of 3 V. The PTD can respond to the UV light from 220 to 340 nm and the peak responsivity is ~ 125A/W at 275 nm. This work is significant for developing high-performance SiC-based bipolar phototransistors. [ABSTRACT FROM AUTHOR]

p+-Si/n-Zn2SiO4 heterojunction diodes were fabricated on Si substrate, and tested as X-ray detector for the first time in this letter. The devices exhibited good rectification properties at dark current, and the dark current density was $\sim 5.6\times 10^{\mathbf {-6}}$ A/cm2 at −40 V. An obvious response to X-ray illumination (generated by bremsstrahlung with a tungsten target with tube voltage 30 kV) was observed at reversed bias, and the photo-to-dark ratio exceeding 480 was achieved. Furthermore, the detector exhibited both photoconductive behavior and photovoltaic behavior to switching X-ray illumination, and response time and recovery time are discussed on both mechanisms. In addition, the detector showed fast response time less than 200 ms and the linear outputs against incident X-ray dose rate from 0.383 Gy/s to 4.596 Gy/s at zero-bias voltage. The results imply that the ultra-wide band gap Zn2SiO4 based junction-type detectors have the potential for passive X-ray dose detection and nuclear battery cell applications. [ABSTRACT FROM AUTHOR]

Vertical Au/ZnO Schottky barrier diodes (SBDs) were fabricated on an n+ Si substrate and tested as X-ray detectors in this paper. The high-resistivity ZnO film-based SBDs had a large effective area about 0.78 cm2 and showed a notable sensitivity about 0.78 uC/Gy for X-ray illumination. The detector with linear outputs achieved an X-ray dose measurement across four orders of magnitude of the dose rate from 3.83 mGy/s to 19.00 Gy/s. The response current to switched X-ray illumination exhibited a repeatable and stable characteristic, and the response current mechanism was given and discussed. The results imply the potential of junction devices based on ZnO material for X-ray dose measurement. [ABSTRACT FROM AUTHOR]

High-resistivity ZnO film-based photoconductive detectors have been fabricated on glass substrate by the magnetron sputtering growth method, and tested as X-ray detectors for the first time in this letter. The devices exhibited a low dark current $\sim ~100$ pA at 40 V bias and a fast transient reproducible response to X-ray illumination (generated by bremsstrahlung with a tungsten target with tube voltage 30 kV) $\sim ~200$ ms, which was mainly attributed to the high resistivity $\sim ~10^{9} \Omega $ cm of the ZnO film deposited in the oxygen atmosphere. The high resistivity was due to the zinc vacancy defects’ compensation with the n-type defects in ZnO film as revealed by photoluminescence spectra. Furthermore, the detector achieved an X-ray pulse detection, and the rise time and full width at half maximum of the outputs signal were $139~\mu \text{s}$ and 0.9 ms at 200 V bias, respectively. Associated with material characterizations, it was demonstrated that the high-resistivity ZnO film detector had the potential to be promising for fast X-ray detection application. [ABSTRACT FROM AUTHOR]

A ZnO nanomaterial-based surface acoustic wave (SAW) ultraviolet (UV) detector is highly desirable for UV radiation detection due to its high sensitivity. In this work, firstly the ZnO nanomaterial-based SAW UV detectors operating at three different frequencies (∼50, ∼100 and ∼200 MHz) were fabricated. Then, four ZnO nanomaterial sensing layers with different thicknesses were synthesized on the SAW UV detectors operating at ∼200 MHz. The morphology, crystallization and photoluminescence of ZnO nanomaterial sensing layers were characterized using the scanning electron microscopy, transmission electron microscopy, x-ray diffraction and fluorescence spectrometer, respectively. The SAW UV detectors based on different operating frequencies and ZnO nanomaterial sensing layer's thicknesses were exposed under UV illumination at a wavelength of 365 nm and their UV responses were measured. The experimental results indicate that the frequency shift of ZnO nanomaterial-based SAW UV detector can be significantly improved by increasing operating frequency or ZnO nanomaterial sensing layer's thickness. Furthermore, the detectors exhibit good selectivity of UV illumination, an ultrahigh UV sensitivity of about 9.6 ppm (µW cm−2)−1 and fast transient properties. The experimental results agree well with the acousto-electric effect theory. What deserves to be noted is that, under a UV intensity of 150 µW cm−2, the frequency shift of the SAW UV detector operating at ∼50 MHz with a thin ZnO nanomaterial sensing layer was only ∼50 kHz while that of the SAW UV detector operating at ∼200 MHz with a thick ZnO nanomaterial sensing layer could reach ∼292 kHz. These results suggest the huge potential applications of ultra-sensitive ZnO nanomaterial-based SAW UV detectors for remote wireless UV and radiation monitoring. [ABSTRACT FROM AUTHOR]

• The 25 µm-thick ZnO film using sputtering method was characterized for X-ray detection applications. • p+-Si/ZnO X-ray detector based on the 25 µm-thick ZnO film shows a high sensitivity of 128 μC∙Gy−1∙cm−2 at − 20 V. • The on-off response is related to the V O defect, which was verified by the transmittance spectrum and the TSC spectrum. [Display omitted] In the field of direct-conversion flat panel X-ray detector, semiconductor with thickness of tens to hundreds microns is needed. In this paper, we demonstrate that thick ZnO semiconductor deposited by RF magnetron sputtering can be candidate for the X-ray detector. The 25 µm ZnO film was prepared by sputtering method under 200 °C and a p+-Si/ZnO X-ray detector based on the thick ZnO film was investigated to explore its X-ray detection properties. The detector shows nonzero short circuit current and open circuit voltage indicating the heterojunction nature of the ZnO film in contact with the p+-Si substrate. The detector shows linear response to the X-ray dose rate and has a high sensitivity of 128 μC∙Gy−1∙cm−2 at −20 V under 30 kV p X-rays indicating its great potential in the flat panel X-ray detector applications. The on-off response of the detector is related to the V O defect in the ZnO film, which can be verified from the transmission spectrum, the thermal stimulated current spectrum, and the photoluminescence spectrum. [ABSTRACT FROM AUTHOR]