Effect of the GaAsP shell on optical properties of self-catalyzed GaAs nanowires grown on silicon

TL;DR

This study demonstrates that coating GaAs nanowires with GaAsP shells significantly enhances their optical emission, enabling bright room-temperature photoluminescence due to suppression of surface states.

Contribution

It provides a detailed analysis of how GaAsP shells improve optical properties of GaAs nanowires grown on silicon, with high crystal quality confirmed by TEM and optical measurements.

Findings

PL enhancement exceeds 2000 times at 10K in core-shell NWs

Bright emission persists at room temperature in core-shell NWs

GaAsP shells suppress non-radiative surface states

Abstract

We realize growth of self-catalyzed core-shell GaAs/GaAsP nanowires (NWs) on Si substrates using molecular-beam epitaxy. Transmission electron microscopy (TEM) of single GaAs/GaAsP NWs confirms their high crystal quality and shows domination of the zinc-blende phase. This is further confirmed in optics of single NWs, studied using cw and time-resolved photoluminescence (PL). A detailed comparison with uncapped GaAs NWs emphasizes the effect of the GaAsP capping in suppressing the non-radiative surface states: significant PL enhancement in the core-shell structures exceeding 2000 times at 10K is observed; in uncapped NWs PL is quenched at 60K whereas single core-shell GaAs/GaAsP NWs exhibit bright emission even at room temperature. From analysis of the PL temperature dependence in both types of NW we are able to determine the main carrier escape mechanisms leading to the PL quench.