Finite-temperature density instability at high Landau level occupancy

We study here the onset of charge density wave instabilities in quantum Hall systems at finite temperature for Landau level filling v > 4. Specific emphasis is placed on the role of disorder as well as on an in-plane magnetic field. Beyond some critical value, disorder is observed to suppress the charge density wave melting temperature to zero. In addition, we find that a transition fi-om perpendicular to parallel stripes (relative to the in-plane magnetic field) exists when the electron gas thickness exceeds approximate to 60 Angstrom. The perpendicular alignment of the stripes is in agreement with the experimental finding that the easy conduction direction is perpendicular to the in-plane field.