Development of new antimony-based heterostructures for electronic devices

Magno, R.; Ancona, M. G.; Bennett, B. R.; Boos, J. B.; Champlain, J. G.; Culbertson, J. C.; Glaser, E. R.; Shanabrook, B. V.; Tischler, J. G. United States

The drive for high-speed low-power electronic devices has motivated our work in developing the molecular beam epitaxial growth of heterostructures composed of antimony-based alloys. The alloys range from those that are lattice matched to InAs to a variety of alloys with lattice constants near 6.3 Å. We frequently use In_zGa_1-zSb for the narrow bandgap component as it is easily grown and it has both high electron and hole mobilities. Based on the work of Vurgaftman et al.¹ we have chosen to use In_xAl_1-xAs_ySb_1-y alloys for the wider bandgap heterostructure component. By varying the In/Al and As/Sb ratios the models suggest it is possible to obtain a variety of alloys with a wide range of bandgaps while remaining lattice matched to the narrow bandgap In_zGa_1-zSb. This allows flexible use of bandgap engineering to optimize device performance. The first alloys of interest were In_0.27Ga_0.73Sb, and several In_xAl_1-xAs_ySb_1-y alloys with a 6.2 Å lattice constant. X-ray, photoluminescence, atomic force microscopy, and Hall Effect were used to determine the properties and quality of the materials. One goal was to develop p-type In_0.27Ga_0.73Sb/n-type In_xAl_1-xAs_ySb_1-y heterojunctions for use in an npn HBT. This is an example of a device where bandgap engineering is important. Large valence band offsets between In_0.27Ga_0.73Sb and lattice matched In_xAl_1-xAs_ySb_1-y alloys are expected,¹ and they are predicted to be largely independent of x and y. Therefore the choice of In_xAl_1-xAs_ySb_1-y alloy can be used to tailor the conduction band offsets to optimize performance while maintaining a large valence band offset.
The results of materials characterization and device experiments will be presented and discussed. Among them will be the results of photoluminescence measurements on several different In_xAl_1-xAs_ySb_1-y/In_0.27Ga_0.73Sb superlattices that were analyzed to determine conduction band offsets ~120-150 meV with x=0.69 and y=0.41. These are in agreement with the expected values. Tests on the development of individual p-n heterojunctions indicate good rectification and ideality factors near 1. HBTs have also been made and tested.
This work is supported by the Office of Naval Research
¹ I. Vurgaftman, J.R. Meyer, and L.R. Ram-Mohan, J. Appl. Phys. 89, 5815 (2001).

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