The Photomagnetoelectric Effect in Mercury Iodide
In order to investigate the transport properties of mercury iodide, measurements of photomagnetoelectric (PME) effect and photoconductivity (PC) have been carried out. The experimental results show the presence of trapping phenomena and a strong dependence of carrier lifetimes on the light injection level. The obtained values of the lifetimes are in the range 10-7-10-6 s.
Photoelectronic properties of HgI2
Abstract In order to investigate hole and electron trapping centers in HgI 2 various photoelectronic techniques, such as the thermally stimulated current (TSC) method, photoconductivity (thermal quenching, TQ, spectral response and intensity dependence). the photovoltaic effect (temperature, wavelength and luminous intensity dependence), have been used. The main results which have been obtained are: (1) two main hole traps at 0.15 eV and 0.43 eV above the valence band are present in all the investigated crystals and dominate the electrical behaviour of HgI 2 ; (2) a change from p-type to n-type conductivity with light intensity is clearly evident, and it depends on selected ingot; (3) level at 0.43 eV seems to behave as a sensitizing center for photoconductivity; (4) the maximum value of the photovoltage, the spectral dependence of the photovoltaic effect and the dependence of photoconductivity on luminous intensity are probably methods to forecast the performances of HgI 2 as an X-ray detector.
Photo-effects in semiconductors
Abstract This review of internal photo-effects will emphasize two particular interests; firstly their use as a powerful opto-electronics technique for studying a wide range of properties of semiconductors, and secondly the possibility of fabricating useful devices for the detection and measurement of radiation in the infrared and visible regions. The most conventional forms of photo-effects are concerned physically with the generation and recombination of free-charge carriers, and with their movements in various structures under the influence of a variety of applied fields. The general theory governing photo-carriers in semiconductors is outlined, and by making appropriate simplifications interesting results can be obtained for different limiting conditions, geometries, applied fields etc. The generation process is closely allied to absorption, and is particularly useful in the study of little-known materials of poor quality. The theory shows that with suitable arrangements it is possible to measure absolute absorption constants from relative studies of photo-conductivity. Generation at higher photon energies is a valuable means of studying collision process. Recombination mechanism, both in bulk materials and on the surfaces, and trapping effects are probably better studied by photo-effects than in any other way. Inhomogeneous (p-n junction) structures are considered with the interests of ultra-high-speed detectors and solar batteries particularly in mind. Less conventional photo-effects which do not involve any change in the numbers of photo- carriers are discussed with reference to intra-band transitions which change the carrier effective masses and free carrier effects where the energy dependence of scattering times causes mobility changes. Finally, consideration is given to radiation pressure effects where neither numbers nor mobility are changed, but carrier distributions are altered by transfer of momentum from the radiation.