Photoconduction of nanoparticle arrays pumped with near 1550 nm pulse lasers

Abstract

When erbium (Er) concentration is greater than ∼7 × 1017/cm3, ErAs nanoparticles with various sizes are formed spontaneously in GaAs epitaxial layer during MBE growth. This letter presents experimental studies on transient photoconduction of ErAs nanoparticle arrays when pumped by laser pulses with wavelengths near 1550 nm. The experimental data suggests the photoconduction may be contributed by two mechanisms. One is extrinsic photoconductivity, where bound electrons from levels of nanoparticles pinned near the middle of GaAs forbidden gap transfer to the conduction band of GaAs (i.e. bound to conduction band). The other is displacement-current conduction traced to photon-assisted polarization of nanoparticles with two quantized energy levels. This investigation explains why these nanoparticle-embedded materials have a higher responsivity to pulsed lasers than continuous wavelength (CW) lasers.