In order to develop a technique for the fabrication of novel low-dimensional heterostructure devices, we study the electronic properties of in situ chlorine etched and epitaxially regrown heterostructures. In our modulation-doped heterostructures, a two-dimensional electron system is located directly at the etched and regrown GaAs/AlGaAs interface. We evaluate the ratio of the classical transport scattering time τt and the single particle relaxation time τs determined from Shubnikov-de Haas oscillations. While the chlorine pressure during the etching process was the same, we compare samples etched at different temperatures. We find that the mobilities μ=eτt/m* exhibit a pronounced maximum of 186,000 cm2/V. An evaluation of the single particle relaxation time τs shows that the ratio of τt/τs also reveals a distinct maximum. Our analysis strongly indicates an etching temperature dependent roughness of the etched and regrown interface.