Volume 99, Issue 4, 15 February 2006
Index of content:
99(2006); http://dx.doi.org/10.1063/1.2171779View Description Hide Description
The recombination property of nitrogen (N)-related acceptor-bound states in has been investigated by photoluminescence(PL), time-resolved PL, and selective PL. Several possible recombination processes were discussed by analyzing the relaxation and recombination properties under large Coulomb interaction. It is strongly suggested that bound exciton emission dominates the recombination process related to the N acceptor. The recombination lifetime is and the binding energy is for N-acceptor-bound exciton at low temperature.
99(2006); http://dx.doi.org/10.1063/1.2172720View Description Hide Description
The structure,Curie temperature, and magnetostriction of polycrystalline crystals were investigated by x-ray diffraction, vibrating-sample magnetometer, and standard strain gauge techniques. It is found that alloys are nearly a single Sm(Zn,Mn) phase with the CsCl-type cubic structure up to . The Curie temperature of alloys quickly increases with increasing Mn when and gradually does in the range of . The substitution of Mn for Zn in the SmZn compound has a marked effect on improving the Curie temperature and makes it reach when . The magnetization of alloys increases with increasing Mn content in the range of and the magnetostriction increases in the range of .
99(2006); http://dx.doi.org/10.1063/1.2172721View Description Hide Description
We provide experimental evidence of the opening of two new pseudogaps in the high energy region of the direction in ZnO inverted opals. The appearance of these new pseudogaps is brought about by the increase of refractive index contrast. The calculated band diagram in the direction, which corresponds to propagation along the (111) crystallographic direction, accounts for the spectral width and position dependence of the pseudogaps on the ZnO fraction present in the opal. To prove this we have performed an optical study by means of reflection and transmission spectroscopy of ZnO inverted opals with different degrees of infiltration. We also study the pseudogap appearing in the highest energy spectral position as a function of sample thickness. In addition, the band engineering developed here allows us to isolate a nondispersive band from the others.
99(2006); http://dx.doi.org/10.1063/1.2173188View Description Hide Description
It is demonstrated that the emission of InAs quantum dots(QDs) capped with GaAsSb can be extended from by increasing the Sb composition of the capping layer from 14% to 26%. Photoluminescence excitation spectroscopy is applied to investigate the nature of this large redshift. The dominant mechanism is shown to be the formation of a type-II transition between an electron state in the InAs QDs and a hole state in the GaAsSb capping layer. The prospects for using these structures to fabricate injection lasers are discussed.
99(2006); http://dx.doi.org/10.1063/1.2173187View Description Hide Description
In this paper we present an approach based on the known radiative recombination rate model to study the dynamics and characteristics of photoluminescence(PL) transitions at room-temperature (RT) regime of GaN thin film. The model states that the dependence of the PL intensity on the laser excitation intensity is in which the value of the exponent reveals whether the PL is due to an exciton or band gap recombination mechanism. We elaborated on the model and studied the temperature behavior of the exponent in the range of in order to explore the recombination type for that range. It was found that at the temperature range just below RT the exponent is a slowly increasing function of temperature and has an average value of , implying a free-exciton recombination mechanism. At the value of the exponent was found to exhibit a step-function-like behavior with a sharp increase from 1.2 to 1.7. At the temperature range just above RT the exponent was found again to be a slowly increasing function of temperature with an average value of , implying that at that temperature range the PL involves mainly band gap transitions. From the temperature behavior of the exponent, the activation energy of the free exciton was inferred to be .