This study reports on tunable quasi-two-dimensional electron gases (q2-DEGs) in oxide heterostructures. The q2-DEGs are formed at the interface between LaAlO3 and SrTiO3, and their conductivity can be modulated by gate voltages through a quantum phase transition from an insulating to a metallic state. The q2-DEGs exhibit high mobility (up to 10^4 cm² V⁻¹ s⁻¹) and high carrier density, making them suitable for high-electron mobility transistor (HEMT)-type field-effect devices. The conductivity of the q2-DEGs depends on the thickness of the LaAlO3 layers, with a critical thickness of 4 unit cells (uc) required for conduction. Below this threshold, the interface is insulating. The q2-DEGs can be tuned by altering the thickness of the LaAlO3 layers, and their properties are influenced by oxygen vacancies and polarity discontinuities. The study also demonstrates that the q2-DEGs can be controlled by electric fields, showing a memory effect where the conductance remains for hours after a gate voltage is removed. The q2-DEGs are found to have high carrier densities and mobilities, and their behavior is similar to those in semiconductor heterostructures. The study highlights the potential of oxide heterostructures for device applications, particularly in oxide electronics, due to their ability to couple with gate fields and electronic degrees of freedom of neighboring complex oxides. The results suggest that these heterostructures could be used to create devices with high on/off ratios and large electric-field responses. The study also identifies the role of SrTiO3 in the memory effect, suggesting that charge excitations in SrTiO3 can influence the properties of the q2-DEG. The findings demonstrate the potential of oxide heterostructures for future electronic devices.This study reports on tunable quasi-two-dimensional electron gases (q2-DEGs) in oxide heterostructures. The q2-DEGs are formed at the interface between LaAlO3 and SrTiO3, and their conductivity can be modulated by gate voltages through a quantum phase transition from an insulating to a metallic state. The q2-DEGs exhibit high mobility (up to 10^4 cm² V⁻¹ s⁻¹) and high carrier density, making them suitable for high-electron mobility transistor (HEMT)-type field-effect devices. The conductivity of the q2-DEGs depends on the thickness of the LaAlO3 layers, with a critical thickness of 4 unit cells (uc) required for conduction. Below this threshold, the interface is insulating. The q2-DEGs can be tuned by altering the thickness of the LaAlO3 layers, and their properties are influenced by oxygen vacancies and polarity discontinuities. The study also demonstrates that the q2-DEGs can be controlled by electric fields, showing a memory effect where the conductance remains for hours after a gate voltage is removed. The q2-DEGs are found to have high carrier densities and mobilities, and their behavior is similar to those in semiconductor heterostructures. The study highlights the potential of oxide heterostructures for device applications, particularly in oxide electronics, due to their ability to couple with gate fields and electronic degrees of freedom of neighboring complex oxides. The results suggest that these heterostructures could be used to create devices with high on/off ratios and large electric-field responses. The study also identifies the role of SrTiO3 in the memory effect, suggesting that charge excitations in SrTiO3 can influence the properties of the q2-DEG. The findings demonstrate the potential of oxide heterostructures for future electronic devices.