The currents through polyethylene single crystals have been measured as functions of voltage and temperature between 200°K and 400°K. The negative resistance phenomena were sometimes observed when thin wire electrodes were used for measuring the current through polyethylene single crystals of 70–300 Å thickness, but their behaviors were different from those described by Roggen. In the case of vacuum evaporated electrodes, however, such phenomenon was not observed. Similar measurements have been done with polyethylene thin films formed by vacuum evaporation. In this case, the negative resistance similar to that described by Hickmott was sometimes observed.
Changes of specific resistance were closely related with the change of crystal thickness in thinner crystals, and the electron transport mechanism was discussed quantitatively with simple theoretical expressions of tunneling effect and Schottky emission.
We demonstrate that the photorefractive effect in GaP crystal at 633 nm can be enhanced using an externally applied dc field and a moving grating. A two-beam coupling gain coefficient of 2.5 cm(-1) and a steady-state phase-conjugate reflectivity of 1.9% were obtained.
Electron traps in plastically bent VPE n-GaAs1-x
P
x
(0≤x≤1) have been investigated using DLTS. While EL2 is dominant at x\lesssim0.5, two additional levels, one a midgap (EP1) and the other a deeper (EP2) level, dominate at x\gtrsim0.55. The energy level of EP1 at x=1.0 is in good agreement with that of the antisite PGa defect level in GaP estimated using ESR studies. EP2 energy levels have little dependence on x. EP1 as well as EL2 shows alloy broadening in DLTS spectra while EP2 remains unchanged. These findings indicate that EL2 and EP1 are due to antisite AsGa and PGa defects, respectively. EP2 is attributable to group V atom site defects.
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