The role of surface states and point defects on optical properties of InGaN/GaN multi-quantum wells in nanowires grown by molecular beam epitaxy

The optical properties of nanowire-based InGaN/GaN multiple quantum wells (MQWs) heterostructures grown by plasma-assisted molecular beam epitaxy are investigated. The beneficial effect of an InGaN underlayer grown below the active region is demonstrated and assigned to the trapping of point defects transferred from the pseudo-template to the active region. The influence of surface recombination is also investigated. For low InN molar fraction value, we demonstrate that AlO (x) deposition efficiently passivate the surface. By contrast, for large InN molar fraction, the increase of volume non-radiative recombination, which we assign to the formation of additional point defects during the growth of the heterostructure dominates surface recombination. The inhomogeneous luminescence of single nanowires at the nanoscale, namely a luminescent ring surrounding a less luminescent centre part points towards an inhomogeneous spatial distribution of the non-radiative recombination center tentatively identified as intrinsic point defects created during the MQWs growth. These results can contribute to improve the performances of microLEDs in the visible range.

Automated summary

The optical properties of nanowire-based InGaN/GaN multiple quantum wells (MQWs) heterostructures grown by plasma-assisted molecular beam epitaxy were investigated, with a focus on the effect of an InGaN underlayer grown below the active region and the influence of surface recombination. It was found that the InGaN underlayer demonstrated a beneficial effect due to the trapping of point defects transferred from the pseudo-template to the active region. Surface recombination was found to be dominated by the formation of additional point defects during the growth of the heterostructure for large InN molar fraction. Inhomogeneous luminescence of single nanowires at the nanoscale highlighted a spatial distribution of non-radiative recombination centers identified as intrinsic point defects created during the growth of MQWs. These findings have implications for improving the performance of microLEDs in the visible range.