We report measurements of diamagnetic shifts for different exciton complexes confined in small InAs quantum dots. The measured diamagnetic responses are sensitive to the number of carriers in the exciton complexes, with systematic differences between neutral excitons, biexcitons, and trions. Theoretical calculations suggest that such systematic differences arise from very different extents of electron and hole wave functions confined in small quantum dots. The measured magnetic response of Coulomb energies is found to vary with the cube of the wave function extent, and can be a sensitive probe to the electron-hole wave function asymmetry.

Carrier dynamics of InAs/ GaAs quantum dots ͑QDs͒ covered by a thin GaAs 1−x Sb x layer were investigated by time-resolved photoluminescence ͑PL͒. Both the power dependence of PL peak shift and the long decay time constants confirm the type-II band alignment at the GaAsSb-InAs interface. Different recombination paths have been clarified by temperature dependent measurements. At lower temperatures, the long-range recombination between the QD electrons and the holes trapped by localized states in the GaAsSb layer is important, resulting in a non-single-exponential decay. At higher temperatures, optical transitions are dominated by the short-range recombination with the holes confined to the band-bending region surrounding the QDs.

Thin InN films were deposited on the (0001) sapphire substrate at various temperatures from 325 to 600 °C by metalorganic vapor phase epitaxy. We used Raman scattering and x-ray diffraction to investigate the film properties and crystalline structures. Significant line broadening, softening and intensity evolution were observed at the growth temperatures between 375 and 450 °C. This can be attributed to the formation of the mixed hexagonal and cubic structures and the related dislocation defects. As the growth temperature is further increased, the hexagonal phase is found to be dominant in the deposited InN film.

We carried out a systematic study on the solid incorporation of InGaN under various growth conditions using metalorganic vapor phase epitaxy (MOVPE). The solid distribution of InGaN was found to be very sensitive to the growth temperature, and the TMGa and TMIn flow rates. Experimental results indicated that at low Ga flow rates InGaN growth is essentially governed by thermodynamic factors, whereas at high growth rate the InGaN solid concentration is determined merely by the vapor composition in the gas phase. In regard to the effect of TMIn flow rates on InGaN growth, it was found that once In droplets form on the surface, the In growth efficiency correspondingly decreases significantly, accounting for the low In solid concentration in InGaN at high TMIn flow rates.

In this study, a sol-gel titanium dioxide (TiO 2 ) was spin-coated on indium tin oxide (ITO) substrate as a sensing membrane for the extended-gate field-effect transistor (EGFET). To improve its sensing properties, the resultant films were thermal annealed at various temperatures. It shows that, as TiO 2 was post-annealed at T a =200 o C for 30 min, a highest pH sensitivity of 79.9 ȝA/pH was derived. As T a > 500 o C, the pH sensitivity was declined substantial to 70.1 ȝA/pH. The sensitivity would further deteriorate to 61.8 ȝA/pH as the annealing time extended to 90 min under identical T a . These phenomena could be attributed to the less surface hydroxyl sites of TiO 2 thin film at elevated T a . X-ray diffractograms indicates that an amorphous titania resides as T a < 200 o C which presents more surface hydroxyl sites than those of crystalline structures at elevated T a . It reveals that the pH sensitivity of EGFET was relied on the density of the surface hydroxyl structures. To employ to the portable sensing devices with desirable pH sensitivity, the post annealing of the asdeposited TiO 2 film is a crucial process.