Dual strategy of modulating growth temperature and inserting ultrathin barrier to enhance the wave function overlap in type-II superlattices

Maximizing wave function overlap (WFO) within type-II superlattices (T2SL) is demonstrated to be important for improving their photoelectric properties, such as optical transition strength and quantum efficiency, which, however, remains a great challenge for now. Herein, the dual strategy of modulating growth temperature and inserting ultrathin AlAs barrier into the AlSb layers is presented to enhance the WFO in InAs/AlSb T2SL. The charge distributions and strain states indicate that moderate growth temperature of 470 °C promotes the As-Sb exchange at AlSb-on-InAs (AOI) interfaces, which would introduce skew of energy band structure towards InAs-on-AlSb (IOA) interface. Such band structure could drive electrons and holes to the IOA interfaces simultaneously, thus resulting in the enhanced WFO. On this basis, insertion of relatively thick (0.3 nm) AlAs layers is found to squeeze more holes towards adjacent interfaces, boosting the WFO further. The InAs/AlSb superlattices with optimized WFO reveal better optical performance, where the peak intensity shows 50% improvement in the PL spectra than the original one. Moreover, a dual-miniband radiative transition mechanism appears in the InAs/AlSb superlattice with relatively thick AlAs intercalation, which helps broaden the wavelength range of the superlattice.