III-V compound semiconductor materials are increasingly important for the development of many modern materials applications and in particular optoelectronic devices. These include materials for laser diodes, light emitting diodes, photovoltaics& photodetectors, avalanche photodiodes, THz emitters& detectors, heterojunction bipolar transistors, and spintronic devices. Over the years several elements from the III-V system have been investigated to advance these material systems in order to persistently progress towards superior devices and to exploit novel material properties for advanced device applications. An example of a relatively unexplored family of semiconductor materials is the alloying of bismuth (Bi), the heaviest naturally occurring group-V element and the heaviest non-radioactive element in the periodic table. Unusual for the heavy elements, Bi is non-toxic and relatively inexpensive and has found application in elemental form in fire-safety systems (due to its low melting point). Furthermore, since spin orbit splitting increases super linearly with atomic number, Bi-alloys have a very large spin orbit splitting compared with conventional semiconductor alloys, thus present interesting opportunities for new types of electronic devices based on electron spin. As a result, III-V bismides offer many new prospects in the area of materials research and the opportunity to develop an innovative class of materials for the expansion of science and technology. Some of the strategic attributes offered by III-V bismide materials are: i) the potential to cover longer near infrared wavelengths on GaAs or InP substrates than either GaInAs or GaAsSb and longer mid and far infrared wavelengths on InAs and GaSb substrates, ii) a uniquely large spin orbit splitting which provides an opportunity for semiconductor spintronic devices, iii) a spin orbit band offset that is typically larger than bandgap energy which provides an opportunity to develop active materials with significantly reduced Auger recombination, iv) a reduced temperature dependence of the bandgap energy that potentially offers improved temperature stability for emitters and detectors, and v) the opportunity for band offset engineering that offers substantial improvement for hole confinement in GaSb based mid IR diode lasers. The technical objective of this Phase I STTR project is the proof of concept for the potential of III-V-Bi devices demonstrated through systematic theoretical modeling of band offsets, band bending, and the influences of temperature and carrier density in materials optimized for mid infrared wavelengths, including the establishment of a reliable database for systematic modeling. To this end a rigorous understanding of the band structure of the novel III-V-Bi material system will be developed. This approach will make it possible to design, guide, and provide feedback on growth, fabrication, and evaluation of semiconductor quantum-confined structures that provide optical gain in the mid infrared atmospheric transmission window. The project will focus on III-As-Sb-Bi semiconductor materials for quantum well lasers in the 3-5 m wavelength range with the potential of watt-level powers for Air Force applications. Antimonide based AlGaInAsSb materials grown on GaSb, are plagued by large Auger losses, poor hole confinement, limited wavelength coverage due to hole confinement, and a miscibility gap in the growth of materials with large indium mole fractions. The utilization of dilute amounts of bismuth offers the opportunity to engineer the valance band offset of these materials for longer wavelength emission with better hole confinement. In particular, the III-V-Bi material system nearly lattice matched to GaSb covers all wavelengths in the 3-5 micron range, making its development attractive for mid infrared lasers. Furthermore, the addition of bismuth can push the spin-off band down in energy reducing the loss processes involving that band.
|Effective start/end date||12/1/14 → 7/31/15|
- DOD-USAF-AFRL: Air Force Office of Scientific Research (AFOSR): $50,000.00
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