Abstract
We demonstrate that a lightly-strained germanium channel (ε_// = -0.41%) in an undoped Ge/Si_0.1Ge_0.9 heterostructure field effect transistor supports a 2D hole gas with mobility in excess of 1×10⁶ cm²/Vs and percolation density less than 5×10¹⁰ cm⁻². This low disorder 2D hole system shows tunable fractional quantum Hall effect at low density and low magnetic field. The low-disorder and small effective mass (0.068m_e) defines lightly-strained germanium as a basis to tune the strength of the spin-orbit coupling for fast and coherent quantum hardware.