Study of deep levels in InAlAsSb grown via organometallic vapor phase epitaxy

Triple junction solar cells lattice matched to InP have the potential to exceed 50% efficiency under AM1.5 500× illumination with a bandgap stack of 1.74 / 1.1 / 0.7 eV. A top cell having 1.74 eV requires development of high-quality InAlAsSb, which currently has very little development effort reported. Preliminary deep-level transient spectroscopy results in p-type InAlAsSb indicate the presence of deep-levels 0.20 eV and 0.44 eV above the valence band with concentration ~10¹⁵ cm^-3. Experiments such as spectral response and dark IV analysis reveal poor solar cell metrics, which may be a direct consequence of the detected defects. The InAlAsSb deep-levels are compared to the better-understood levels found in InAlAs, however, no evidence of a correlation is found.