Electrical instabilities in GaAs/AlGaAs quantum wells: acoustoelectric effects?

Large oscillations of the current in non-degenerate n-type GaAs/AlGaAs quantum wells have been observed under a range of conditions below room temperature. In the case of low electron concentration in a MQW sample the oscillations were damped and the period corresponded to the transit time for transversely polarised acoustic waves. Accompanying oscillations of photoluminescence are also observed, and the electron temperature is seen to drop with time. In the case of a degenerate single-quantum-well sample the oscillations were continuous and the period was a factor about eight shorter than the acoustic transit time. All samples were cut and contacted such that current flowed along a (110) direction.