Nuclear magnetic resonance studies of spin and strain phenomena in nanohole GaAs/AlGaAs quantum dots

This thesis details experimental measurements performed on III-V semiconductor quantum dots, with the main body of work on nanohole GaAs/AlGaAs quantum dots. Through the use of optically detected nuclear magnetic resonance (NMR) and micro-photoluminescence, the components of the gradient elastic tensor, an important material parameter, are determined for GaAs. These values are $S_{11, ^{69}\text{Ga}} =\ $ \SI{-22.2 +- 1.1 e21}{\volt\per\metre\squared}, $S_{11, ^{75}\text{As}} = \ $ \SI{23.9 +- 1.1 e21}{\volt\per\metre\squared}, with $\left(\frac{S_{44}}{S_{11}}\right)_{^{75}\text{As}}$ being in the range of \numrange{1.20}{2.36} and $\left(\frac{S_{44}}{S_{11}}\right)_{^{69}\text{Ga}}$ being in the range of \numrange{-0.88}{-.11}. These values are significantly different to that of the previous work, however, the ratio of the first components for the two nuclei, $\frac{S_{11, ^{69}\text{Ga}}}{S_{11, ^{75}\text{As}}}$, is in close agreement with the previous work, with other derived material parameters being in agreement with the accepted values. The second component of the gradient elastic tensor, $S_{44}$, is found to be in close agreement for one nuclei, with a factor of \num{2} difference for the other nuclei. We conclude that the previous work had unrecognised systematic errors that impacted their results. We study two GaAs/AlGaAs samples with different barrier thicknesses, using NMR and micro-photoluminescence, and observe unexpected up-conversion and dynamic nuclear polarisation phenomena in both samples, one of which was measured with and without externally applied stress. One of the unexpected phenomena, up-conversion, has its origin isolated to three potential impurities / defects in two possible locations in the sample. The other unexpected phenomena, relating to nuclear polarisation, are discussed in depth with their potential origins being presented. In addition to this, the fabrication of Schottky diodes for charge control of InGaAs quantum dot samples is detailed with the initial characterisation, through photoluminescence spectroscopy, being performed to identify the quantum dot states and charge plateaus.