This is the author accepted manuscript. The final version is available from AIP via http://dx.doi.org/10.1063/1.4919053. ; We report magnetotransport measurements of a SiGe heterostructure containing a 20?nm p-Ge quantum well with a mobility of 800?000?cm2 V?1 s?1. By dry etching arrays of wires with widths between 1.0??m and 3.0??m, we were able to measure the lateral depletion thickness, built-in potential, and the phase coherence length of the quantum well. Fourier analysis does not show any Rashba related spin-splitting despite clearly defined Shubnikov-de Haas oscillations being observed up to a filling factor of ??=?22. Exchange-enhanced spin-splitting is observed for filling factors below ??=?9. An analysis of boundary scattering effects indicates lateral depletion of the hole gas by 0.5???0.1??m from the etched germanium surface. The built-in potential is found to be 0.25???0.04?V, presenting an energy barrier for lateral transport greater than the hole confinement energy. A large phase coherence length of 3.5???0.5??m is obtained in these wires at 1.7?K. ; This work was supported by the EPSRC funded ?Spintronic device physics in Si/Ge heterostructures? EP/J003263/1 and EP/J003638/1 projects and a Platform Grant No. EP/J001074/1.