Fast two-stage protector against electromagnetic pulse based on electroresistance effect in polycrystalline La-Sr(Ca)-Mn-O films

The electroresistance (ER) effect in polycrystalline films of La0.83Sr0.17MnO3 and La0.7Ca0.3MnO3 was investigated in the temperature range of (5 – 290) K using high power sub-nanosecond rise time electrical pulses with amplitude up to 1 kV. It was obtained that conductance vs. voltage dependences are nonlinear and could be well fitted by empirical formula G = G0 + Gα · Uα; where G is conductance, U is the voltage applied across the sample, G0 is the conductance at low voltage, and Gα and α are the parameters related to the electrical transport mechanism. Parameters α for La-Ca-Mn-O and La-Sr-Mn-O were 1.5 and 1.33 respectively. It was obtained that there are two regions of the electroresistance vs. temperature dependence for both films: low temperature region where ER exhibits very slow dependence on temperature and high temperature region where ER significantly decreases with temperature. It was demonstrated that polycrystalline manganite films can be used for the development of protectors against short electromagnetic pulse (EMP), and fast twostage protector operating at cryogenic temperatures (80 K) is proposed

High performance type-II InAs/GaSb superlattice infrared photodetectors with a short cut-off wavelength

This work investigates the potential of InAs/GaSb superlattice detectors for the shortwavelength infrared spectral band. A barrier detector structure was grown by molecular beam epitaxy and devices were fabricated using standard photolithography techniques. Optical and electrical characterisations were carried out and the current limitations were identified. The authors found that the short diffusion length of ~1.8 µm is currently limiting the quantum efficiency (double-pass, no anti-reflection coating) to 43% at 2.8 µm and 200 K. The dark current density is limited by the surface leakage current which shows generation-recombination and diffusion characters below and above 195 K, respectively. By fitting the size dependence of the dark current, the bulk values have been estimated to be 6.57·10ˉ⁶ A/cm² at 200 K and 2.31·10ˉ⁶ A/cm² at 250 K, which is only a factor of 4 and 2, respectively, above the Rule07

Two-step etch in n-on-p type-II superlattices for surface leakage reduction in mid-wave infrared megapixel detectors

This work investigates the potential of p-type InAs/GaSb superlattice for the fabrication of full mid-wave megapixel detectors with n-on-p polarity. A significantly higher surface leakage is observed in deep-etched n-on-p photodiodes compared to p-on-n diodes. Shallowetch and two-etch-step pixel geometry are demonstrated to mitigate the surface leakage on devices down to 10 μm with n-on-p polarity. A lateral diffusion length of 16 μm is extracted from the shallow etched pixels, which indicates that cross talk could be a major problem in small pitch arrays. Therefore, the two-etch-step process is used in the fabrication of 1280 × 1024 arrays with a 7.5 μm pitch, and a potential operating temperature up to 100 K is demonstrated