Far-infrared photoconductivity measurement at 1.5 to 10 K confirms the existence of an A+ center and an A+ related complex in zinc doped germanium. Hole binding energies of the A+ center and the A+ related complex are estimated as about 2 and 7 meV, respectively, from the lower energy threshold of photoconductivity and the dependence of photoconductivity on temperature.
Nucleation and decay kinetics of electron-hole droplets are investigated by photoluminescence measurements of germanium crystals doped with deep impurities, Be, Zn or Te, as well as with a shallow impurity Sb. Deep impurities decelerate the formation of droplets in contrast to shallow impurities, which accelerate the formation. The lifetime of droplets is shortened by doping deep impurities. Far-infrared absorption of droplets in Zn-doped germanium is also discussed.
Luminescence spectra have been measured in TlBr doped with iodine ions under the pulse light excitation. Two broad emission bands were observed at 2.2 eV and 2.45 eV. The emission band at 2.2 eV decayed nonexponentially and was attributed to the radiative recombination of trapped holes and electrons from the measurements of the decay properties and the spectral shape of the emission band. The emission band at 2.45 eV decayed with two time constants of 0.5 ms and less than 10 ns. The fast decay component was assigned to the radiative annihilation of the singlet-triplet mixed state of the selftrapped exciton. The slow decay component was attributed to the triplet state of the exciton, which will be weakly allowed by an iodine ion.
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