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We investigate the nature of transport and ferromagnetic properties of the epitaxial GaAs structure with the Mn δdoped layer. To modify the properties of the structure electrically active radiation defects are created by irradiation with 50 keV helium ions and a fluence in the range of 1 × 10 11 -1 × 10 13 cm -2 . The investigations show that transport properties of the structure are determined by two parallel conduction channels (the channel associated with hole transport in a valence band and the channel associated with electron transport in the Mn-related impurity band) and that ferromagnetic properties are determined by electrons localized at allowed states within the Mn impurity band. The ferromagnetic properties of the Mn δ-layer region cannot be affected by the closely located InGaAs quantum well, since the presence of quantum well has negligible influence on the Mn impurity band filling by electrons.

Doping with donor and acceptor impurities is an effective way to control light emission originated from quantum-size effect in Si nanocrystals. Combined measurements of photoluminescence intensity and kinetics give valuable information on mechanisms of the doping influence. Phosphorus, boron, and nitrogen were introduced by ion implantation into Si+ -implanted thermal SiO2 films either before or after synthesis of Si nanocrystals performed at Si excess of about 10 at.% and annealing temperatures of 1000 and 1100 degrees C. After the implantation of the impurity ions the samples were finally annealed at 1000 degrees C. It is found that, independently of ion kind, the ion irradiation (the first stage of the doping process) completely quenches the photoluminescence related to Si nanocrystals (peak at around 750 nm) and modifies visible luminescence of oxygen-deficient centers in the oxide matrix. The doping with phosphorus increases significantly intensity of the 750 nm photoluminescence excited by a pulse 337 nm laser for the annealing temperature of 1000 degrees C, while introduction of boron and nitrogen atoms reduces this emission for all the regimes used. In general, the effective lifetimes (ranging from 4 to 40 micros) of the 750 nm photoluminescence correlate with the photoluminescence intensity. Several factors such as radiation damage, influence of impurities on the nanocrystals formation, carrier-impurity interaction are discussed. The photoluminescence decay is dominated by the non-radiative processes due to formation or passivation of dangling bonds, whereas the intensity of photoluminescence (for excitation pulses much shorter than the photoluminescence decay) is mainly determined by the radiative lifetime. The influence of phosphorus doping on radiative recombination in Si quantum dots is analyzed theoretically.

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