Characterization of Short-Wavelength-Selective a-Si:H MSM Photoconductors for Large-Area Digital-Imaging Applications
Photoconductor-type photodetectors are attractive as sensors due to their compatibility with thin-film-transistor (TFT) fabrication processes. Since they exhibit photogain, photoconductor detectors have better or comparable responsivity and quantum efficiency (QE) compared to p-i-n photodiodes. In this paper, the operation of metal-semiconductor-metal photoconductor-based photodetectors using aluminum electrodes and thin hydrogenated amorphous-silicon (a-Si) films is investigated. The experimental results of photocurrent measurements, as well as the responsivity and QE for different a-Si film thicknesses, bias voltages, and electrode gaps, are presented. Integration with TFT fabrication and its application in large-area digital imaging are discussed.
Blue-Light-Sensitive Phototransistor for Indirect X-Ray Image Sensors
A thin-film phototransistor with a peak wavelength sensitivity of 420 nm was fabricated by integrating a bilayer hydrogenated-amorphous-silicon absorber with a nanocrystalline-silicon channel layer. The phototransistor response at λ = 420 nm was about 92 mA/W for an incident power density of 0.16 mW/cm2. A readout pixel circuit having a single transistor, acting as both the sensing and switching elements, is proposed to demonstrate the device potential for high-resolution pixelated X-ray imaging arrays. Simulation results reveal less than 150 μs to read out the pixel voltage with a storage capacitor of 1 pF. Thus, a frame rate of about 75 ms is predicted for a 500 × 500 pixel imaging array. Transient photocurrent measurements yield on (rise) and off (fall) times of 0.6 and 3 ms, respectively, verifying the requirements for a high frame rate.
On the ontology of particle mass and energy in special relativity
Einstein claimed that the fundamental dynamical insight of special relativity was the equivalence of mass and energy. I disagree. Not only are mass and energy not equivalent (whatever exactly that means) but talk of such equivalence obscures the real dynamical insight of special relativity, which concerns the nature of 4-forces and interactions more generally. In this paper I present and defend a new ontology of special relativistic particle dynamics that makes this insight perspicuous and I explain how alleged cases of mass–energy conversion can be accommodated within that ontology.