TUNNELING CURRENT THROUGH SI DONOR LEVEL IN GAAS ALAS SINGLE-BARRIER DIODES/

The tunneling current in Si planar-doped GaAs/AlAs single-barrier diod es is studied. First, we determine the effects of growth interruption and doped Si impurities on the tunneling current. We observe excess cu rrent for a sample with Si doping during growth interruption (Si plana r doping) in the AlAs barrier, while we do not observe it for a sample which was subjected only to growth interruption. This result shows th at the excess current is not caused by impurities incorporated from th e background during growth interruption but by the intentional doping of Si impurities, We then examine the dependence of the excess current on Si concentration. The excess current increases as the Si concentra tion increases. This result provides further evidence that Si impuriti es introduce paths for the flow of the excess current. In the conducta nce-voltage characteristics, we observe a peak corresponding to the ex cess current. This peak suggests that the excess current Rows through zero-dimensional states, Finally, we discuss the Si donor levels as po ssible origins of the excess current. The shallow donor level is proba bly responsible for the excess current.