We experimentally study the phase diagram of the integer quantized Hall effect, as a function of density and magnetic field. We used a two-dimensional hole system confined in a Ge/SiGe quantum well, where all energy levels are resolved, because the Zeeman splitting is comparable to the cyclotron energy. At low fields and close to the quantum Hall liquid-to-insulator transition, we observe the floating up of the lowest energy level due to the disorder broadening, but no floating of any higher levels, rather a merging of these levels into the insulating state. For a given filling factor, only direct transitions between the insulating phase and higher quantum Hall liquids are observed as a function of density. Finally, we observe a peak in the critical resistivity around a filling factor of 1.

• Received 5 June 2000

DOI:https://doi.org/10.1103/PhysRevB.62.6940