| Carrier transmission coefficient in quantum dot (QD)/polymer ensembles was calculated and minibands indicated by transmission coefficient peaks facilitate charge transport in novel designs of optoelectronic devices using QD and polymer superlattices, which are also robust to QD distribution fluctuations. The second work investigated a single-photon detector based on a GaN double barrier resonant tunneling diode. The current-voltage characteristics at 0 K were studied and negative differential resistance was observed with a large peak-to-valley ratio. The well width was varied to investigate its effect on the negative differential resistance and the magnitude of the current was shown to also depend on the doping level of the contact regions. In the third part, the thermal conductivity of carbon nanotubes was discussed. A continuum model was used to calculate the thermal conductivity of CNTs along the tube axis. It was shown that shorter CNTs have lower thermal conductivity at higher temperatures. So, short CNTs at elevated temperatures may improve the thermoelectric figure of merit, which makes conversion of waste heat to electricity more efficient. The c-axis thermal conductivity of graphite was explored using quantum confinement. Low thermal conductivity was obtained and can be used to realize high electrical and thermal conductivity ratios by stacking individual sheets of graphite along the c-axis direction. |
