Hysteresis and spikes in the quantum Hall effect

We observe sharp peaks and strong hysteresis in the electronic transport of a two-dimensional electron gas (2DEG) in the region of the integral quantum Hall effect. The peaks decay on time scales ranging from several minutes to more than an hour. Momentary grounding of some of the contacts can vastly modify the strength of the peaks. These features disappear under application of a negative bias voltage to the backside of the specimen. We conclude that a conduction channel parallel to the high mobility 2DEG is the origin for the peaks and their hysteretic behavior.