INTERFACE STUDIES OF ALXGA1-XAS-GAAS HETEROJUNCTIONS

Ion-depth profiling with Auger electron spectroscopy has been used to measure the interface width of MBE, VPE, and LPE AlxGa 1-xAs-GaAs heterojunctions purposely fabricated to minimize interface width. By profiling the MBE structures with 250-eV Ar+ ions, it was possible to experimentally measure an interface width (10-90% Al p-p height) of ∼15 Å. The measured interface width of VPE and LPE Al xGa1-xAs-GaAs was found to be ∼65 and 100 Å, respectively. Since rectification has not in the past been observed in n-n AlxGa1-xAs-GaAs heterojunctions, n-n AlxGa 1-xAs-GaAs heterojunctions were fabricated in this study to enhance the presence of the conduction-band discontinuity (enhancing any possible rectification) by growing these heterojunctions from lightly doped (10 15-1016 cm-3) material; however, these heterojunctions did not exhibit rectification, in agreement with previous studies. The interface widths of these samples were then measured and found to be much smaller than present theories require to remove the barrier. Since compositional grading is not large enough to explain the absence of rectification, several alternative explanations to the absence of rectification are discussed.