| In this dissertation, results of low temperature (20mK) transport measurements in 200x200 quantum dot arrays are presented and discussed. The devices are made of GaAs/AlGaAs two dimensional electron gas (2-DEG) structures, grown by Molecular Beam Epitaxy (MBE). The 2-DEG is processed using electron beam lithography and etching techniques to fabricate the arrays in which coupling between dots and electron density are controlled by a single gate. The current-voltage (I-V) characteristics of the arrays have two main features: (a) There are discontinuous and hysteretic jumps in the current, or "switching events". Multiple switching events result in a hierarchy of hysteresis loops. This is the first observation of such multi-stabilities in a semi-conducting quantum dot array. (b) In the non-hysteretic regime the current is zero below a threshold voltage, and above a threshold voltage increases obeying a power law with an exponent {dollar}zetasim1.5{dollar}. As the temperature is raised, the threshold voltage decreases and above a critical temperature, the array goes through a metal-insulator transition such that the linear response conductance becomes finite. This is the first observation of a conduction threshold and metal-insulator transition in a semi-conducting quantum dot array. By changing the gate voltage V{dollar}rmsb{lcub}g{rcub}{dollar}, it is possible to move between the hysteretic and non-hysteretic regimes.; These features in the I-V curves are very similar in appearance to those observed in a variety of other strongly interacting systems, including sliding charge density waves (CDW) and magnetically induced Wigner solid (MIWS) systems. In a control dot fabricated on the same chip, a single hysteresis loop accompanied by a single switching event is also observed.; In Chapter 2, device fabrication and experimental setup are described. In Chapters 3 and 4, the experimental data are presented. In Chapter 5, possible mechanisms for hysteresis, such as charge exchange in the form of a leakage current to the gate, DX centers, occupation of impurity states, and electron heating are discussed. Finally, the experimental results are compared to the characteristics of CDW and MIWS systems in Sec. 5.6. |
