Professor Robert Taylor

Abstract:

We have investigated the optical properties of GaN nanorods with different diameters by microphotoluminescence (PL) and time-resolved PL measurements grown on (111) Si substrates by using radio-frequency plasma-assisted molecular-beam epitaxy. In order to confirm the formation of the GaN nanorods and their physical dimension, we employed high resolution scanning electron microscopy. As the diameters of the nanorods decreased, the donor bound exciton (D 0X) emission, which is mainly observed at low temperature for samples with larger diameters, rapidly quenched compared with the free exciton (FX). The activation energy of the FX for GaN nanorods with different diameters was also evaluated. The decay times are a few tens of ps for both the D0X and the FX transitions. The overall decay times decrease linearly with decreasing average diameter of the nanorods. Time-resolved PL studies show that surface recombination is dominant in determining the excitonic dynamics. Copyright © 2009 American Scientific Publishers All rights reserved.

Abstract:

Time-integrated and time-resolved microphotoluminescence studies were carried out on Inx Ga1-x N quantum disks embedded in GaN nanocolumns grown by molecular beam epitaxy. Emission at ∼3.33 eV from confined states was detected and observed to blueshift with excitation power; a result of charge screening and the quantum confined Stark effect. Due to the reduced band bending and resulting increased overlap of the confined electron and hole wave functions, the lifetime of the emission was measured to decrease with increasing excitation power. The saturation of the blueshift and lifetime reduction follows that of the peak intensity, indicating a Stark screening process. © 2009 American Institute of Physics.