Far-infrared measurements of intersubband absorption spectra of /i-inversion layers in (100) Si metal-oxide-semiconductor field-effect transistors with mobile positive ions in the oxide have been carried out between 4.2 and 70 K. Results provide direct evidence for screening of localized states in this quasi two-dimensional electronic system as well as the existence of long band tails and impurity bands at low electron densities associated with subbands due to both the inequivalent conduction-band valleys.
The excess currents generated in anthracene crystals under x radiation have been measured as a function of x-ray intensity, electric field, and temperature. The currents were linear with respect to absorbed dose rate and electric field. A sensitivity of 7.1±0.7×10−12 C/cm2·rad at a field strength of 630 V/cm was obtained. The mobility, lifetime product, μτ, was 9.9±0.9×10−8 cm2/V. The photocurrent was observed to increase with increasing temperature and exhibited two different activation energies, one below 250°K and a second above 250°K. The magnitude of these energies decreased with increasing dose rate. The temperature behavior may be explained in terms of exciton theory or may be due to changes in carrier mobility.
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