GaN1-xSbx highly mismatched alloys grown by low temperature molecular beam epitaxy under Ga-rich conditions

The electronic structure of the conduction and valence bands of highly mismatched alloys (HMAs) such as GaN_1-xSb_x are well described by the band anticrossing model. The properties of this alloy, which has a large band gap range and controllable valence band positions, make it a candidate material for efficient solar energy conversion devices. We have examined the growth and structural properties of amorphous and crystalline GaN_1-xSb_x. These HMAs were grown by low temperature molecular beam epitaxy (MBE) under Ga-rich conditions. While there is a monotonic linear increase of Sb incorporation with Sb overpressure, there was no obvious dependence of Sb incorporation with growth temperature for the range of 10-470 C. At growth temperatures lower than 100 C, GaN_1-xSb _x HMAs lose crystallinity and become amorphous for Sb compositions at or exceeding ∼5%. Ga-rich growth resulted in strong absorption at energies as low as 1 eV for GaN_1-xSb_x alloys of all compositions. The strong low energy absorption may arise from a Ga-related defect band. © Published by Elsevier B.V.