Laser induced photothermal effects on InAs nanowires: tuning the hole density

Optical control of the hole density in InAs nanowires is achieved by simultaneous photogeneration and local heating, varying the laser power during Raman measurements. We have derived the laser induced temperature increase from the Raman line-shape analysis. As a result of laser heating, an oxide layer is formed on the surface of the nanowire, which acts as a "photogating layer" (PGL). Upon light illumination, photogenerated electrons trapped in the PGL form a built-in electric field to deplete the free electrons in the InAs core, thus the hole density increases in the InAs with the increase of laser induced photothermal effects. This phenomenon is demonstrated by monitoring the coupled hole plasmon-LO phonon (CPLP) mode. The values of the hole density have been estimated from a full line-shape analysis of the Raman spectra recorded at different laser powers. Our study shows a significant correlation between the oxide layer thickness and the hole density. These findings open up an optical way to the simultaneous manipulation and monitoring of the carrier density in nanowires.