The focus of this thesis is the study of electron transport erostructures in GaAs/ AlGaAs hetapplying free of intentional dopants, and where free electrons are obtained by contacts a suitable electric field. Optimisation of the fabrication process for ohmic enabled 2DEGs formed at heterointerfaces contacted. just 30nm below the surface to be obtained In addition, ohmic contacts with resistances of less than 50 ohms can be in deeper induced 2DEGs. vices. The transport experiments discussed are done in both 2D and in mesoscopic de- In 2D transport, a method of determining the different background concentrations impurity in AlGaAs and GaAs in an undoped wafer was developed. In addition, undoped it was found that bias cooling and illumination have effects on the electron mobility of 2DEGs. An investigation several into the v = 5/2 fractional quantum hall state was attempted at gap was electron densities on a high mobility undoped sample. The measured activation less than lOOmK, even at the highest density. However, electron this may be due to the temperature, which was unknown, being a lot higher than the thermometer reading. Mesoscopic devices measured quantum included quantum dots and quantum wires. The and dots were made on 2DEGs at 30nm, 60nm and llOnm below the surface, it was possible show to observe the weak coupling regime in all of them. These devices reproducible characteristics from device to device and from cooldown Stability to cooldown. measurements 2DEGs were show that the quantum dot devices on the 60nm and llOnm more stable against random telegraph signal noise as compared only 30nm to those each depth. deep. A series of bias cooling experiments was also done on one sample from Preliminary deep results are slightly contradictory, with the 30nm and llOnm devices becoming more noisy with bias cooling, as compared no bias, while to a cooldown with 60nm deep devices are quieter with a bias cooldown. Quantum wires made on 60nm and 300nm deep 2DEGs demonstrated ment, lD confinesample. and the zero bias anomaly effect was also seen at 300mK in the 60nm deep The final section offers some possibilities some very for future experiments which would give interesting insights into electron transport. An appendix detailing the fabrication steps is provided.