OBSERVATION OF MULTIQUANTUM WELL STRUCTURE IN AIR USING A SCANNING TUNNELING MICROSCOPE

We investigated GaInAs/InP and AlAs/GaAs multiquantum well (MQW) structures in air using a scanning tunneling microscope (STM). We obtained clear corrugated images of MQWs with nanometer resolution. These corrugations come not from a topological difference but from the difference between the tunneling conductance of the well layers to the tip and that of the barrier layers to the tip. Also the STM images are affected by various factors such as contamination and humidity in the air. We observed degradation of the STM images which might be due to the surface oxidation accelerated by the tunneling current. The degradation rate of the AlAs/GaAs MQWs was much larger than that of the GaInAs/InP MQWs. This phenomenon is interesting from the viewpoint of nanometer scale processing. © 1990, American Vacuum Society. All rights reserved.