IMAGING OF DOMAINS AND CURRENT FILAMENTS IN GAAS ALXGA1-XAS MULTIQUANTUM WELLS/

The field contrast mode of a scanning electron microscope has been use d to image high-field domains and current filaments in GaAs/AlxGa1-xAs multi-quantum wells. In samples where negative differential resistanc e and current instabilities occur, high-field domains form. However, t hese domains are shown to be either stationary or propagating slowly a long the samples, in stark contrast to the case in bulk material. In s amples where n-type negative differential resistance, caused by either real-space transfer or intervalley transfer, is inhibited, high-field domains do not form. In the case of moving domains they are shown to annihilate before reaching the anode, probably by a lateral dissipativ e mechanism. In samples where s-type negative differential resistance occurs current filaments are shown to form, which leads to the irrever sible destruction of the material.