NUSOD 2016 Preview: Electronic properties of polytype GaAs superlattices
GaAs can be considered as the prototype compound semiconductor and is used for a wide range of applications including infrared light emission, acoustic sensing, transistor technology and photovoltaics. Nanowires (NWs) made from GaAs commonly exhibit polytypism, i.e., some segments of the NW crystallize in the zincblende (ZB) and others in the metastable wurtzite (WZ) crystal structure, thus turning the NW into a crystal-phase nanostructure. While the electron states of the ZB phase are principally derived from a single conduction band (CB), two energetically close bands exist in the WZ modification.
In previous studies, the CB in polytype GaAs nanostructures has been treated using hybrid-band models, where the effective masses of the lowest CB in each crystal phase were used in a single-band approach, and band symmetries were considered only for the optical properties. Our approach takes into account both CBs explicitly, resulting in two individual, spatially intersecting potentials. The figure shows the energies of the four energetically lowest electron states as a function of the thickness of the WZ and ZB segments. Black lines indicate a state to be of Γ6,Γ7 character, red lines indicate a Γ8 character. Our model provides possible explanations for different discrepancies found in previous experimental and theoretical studies. More details will be presented at the NUSOD 2016 Conference in Sydney (MC1).