  The reproducible operation of quantum electronic devices is a key requirement
for future quantum information processing and spintronics applications.
Traditionally quantum devices have been fabricated from modulation doped
heterostructures, where there is an intrinsic lack of reproducibility due to
the random potential from ionized donors. Here we show that we can greatly
improve reproducibility over modulation doped devices by using a completely
undoped architecture, with superior uniformity in the confinement potential and
more consistent operating voltages for both electron and hole devices. Our
results demonstrate that undoped heterostructures have significant advantages
over modulation doping for reproducible manufacturing of quantum devices.
