Using time-resolved photoluminescence spectroscopy, we show that two-exciton Auger recombination dominates carrier recombination and cooling dynamics in CdSe nanoplatelets, or colloidal quantum wells. The electron-hole recombination rate depends only on the number of electron-hole pairs present in each nanoplatelet, and is consistent with a two-exciton recombination process over a wide range of exciton densities. The carrier relaxation rate within the conduction and valence bands also depends only on the number of electron-hole pairs present, apart from an initial rapid decay, and is consistent with the cooling rate being limited by reheating due to Auger recombination processes. These Auger-limited recombination and relaxation dynamics are qualitatively different from the carrier dynamics in either colloidal quantum dots or epitaxial quantum wells.

In the present work, we address the open question of the contribution from threading dislocations to the problem of unintentional n-type conductivity exhibited by indium nitride through an examination of the effect that positively charged dislocation lines have on the transverse electron mobility within this material. Assuming that the threading dislocation lines within indium nitride act as a source for free electrons, the screening associated with the positively charged threading dislocation lines is evaluated. The impact this screening has on the dislocation limited electron mobility within this material is then considered. Our results indicate that one of the implications of attributing a donor character to the threading dislocation lines within indium nitride would be a strong non-uniformity in the free electron concentration in the plane of growth of this semiconductor. This contrasts dramatically with the case of gallium nitride.

We employ Monte Carlo simulations of the electron transport that occurs within the two-dimensional electron gas formed at a ZnO/ZnMgO heterojunction. Steady-state and transient electron transport results are presented. We find that at high fields, increases in the free electron concentration result in decreases in the electron drift velocities.

We determine the role that a two-dimensional electron gas, formed at a ZnMgO/ZnO heterojunction, plays in shaping the corresponding temperature dependence of the low-field electron Hall mobility. This analysis is cast within the framework of the model of Shur et al. [M. Shur et al., J. Electron. Mater. 25, 777 (1996)], and the contributions to the mobility related to the ionized impurity, polar optical phonon, piezoelectric, and acoustic deformation potential scattering processes are considered, the overall mobility being determined through the application of Mathiessen's rule. The best fit to the ZnMgO/ZnO experimental results of Makino et al. [T. Makino et al., Appl. Phys. Lett. 87, 022101 (2005)] is obtained by setting the free electron concentration to 3×1018 cm−3 and the ionized impurity concentration to 1017 cm−3, i.e., within the two-dimensional electron gas formed at the heterojunction, the free electron gas concentration is a factor of 30 times the corresponding ionized impurity concentration. How this enhanced free electron concentration influences the contributions to the low-field electron mobility corresponding to these different scattering processes is also examined. It is found that the enhanced free electron concentration found within the two-dimensional electron gas dramatically decreases the ionized impurity and piezoelectric scattering rates and this is found to increase the overall low-field electron Hall mobility.

Within the framework of a grand partition function approach, we develop a four-state model for the analysis of occupancy for dislocation defects within uncompensated n-type wurtzite gallium nitride and compare the obtained results with those determined using the energy minimization and free energy minimization approaches of Read [W. T. Read, Jr., Philos. Mag. 45, 775 (1954)]. The advantages of this particular formulation are its simplicity, the fact that we can now consider both p-type and n-type materials, and the fact that it allows for the consideration of more complex core structures. The sensitivity of the results to variations in the electron-electron interactions within a given dangling bond are considered and found to be relatively minor for the case of n-type doping.