A two-step process consisting of low temperature growth followed by rapid thermal annealing is demonstrated for Ru/(Pb,La)(Zr,Ti)O3 (PLZT)/Ru ferroelectric capacitors directly on silicon. PLZT is a promising material for Gbit-scale ferroelectric memories, but its growth on silicon has proved challenging. The two-step process is designed to enable nucleation of perovskite phase PLZT while limiting diffusion which often leads to device failure. Minimization of stress and interdiffusion during film growth were necessary to optimize the remanent polarization. (Pb-4%La)(Zr0.3Ti0.7)O3 capacitors with remanent polarizations up to 17 μC/cm2 were grown on Ru/Si at 400 °C and 50 mTorr O2 using pulsed laser deposition. Direct high temperature growth (>600 °C) was not possible due to interface reactions, and film cracking was observed at low temperatures as well as at high and low oxygen pressures.
Extended long wavelength response to ~200 µm (50 cm -1 ) has been observed in Ge:Sb Blocked Impurity Band (BIB) detectors with N D ~ 1 x 10 16 cm -3 . The cut-off wavelength increases from 150 µm (65 cm -1 ) to 200 µm (50 cm -1 ) with increasing bias. The responsivity at long wavelengths was lower than expected.This can be explained by considering the observed Sb diffusion profile in a transition region between the blocking layer and active layer. BIB modeling is presented which indicates that this Sb concentration profile increases the electric field in the transition region and reduces the field in the blocking layer. The depletion region consists partially of the transition region between the active and blocking layer, which could contribute to the reduced long wavelength response. The field spike at the interface is the likely cause of breakdown at a lower bias than expected.
Epitaxial germanium layers doped near the metal–insulator transition were grown by liquid phase epitaxy from a Pb melt. Far-infrared absorption was measured between ∼20 cm−1 and 150 cm−1. Linear optical absorption coefficients were determined for Ge:Sb in the doping range of 9.0×1014 cm−3<ND<6.7×1016 cm−3. The peak absorption was found to increase linearly with dopant concentration as expected. The absorption at ∼50 cm−1 increased superlinearly with Sb concentration as a result of impurity banding. The optimal Sb concentration for extended far-infrared photoconductive response (λ>200 μm) in blocked impurity band detectors is discussed.
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