Plasmon energy from strained GaN quantum wells

Abstract

Monochromated valence electron energy-loss spectroscopy in a transmission electron microscope has been used to study plasmon energy from strained GaN quantum wells. The width of studied wells was 4 nm, 3 nm, and 2 nm, respectively. A highly resolved line-spectrum recording shows a shift with respect the GaN bulk-value of the plasmon peak as a function of the width of the quantum well. This shift is explained by considering three major effects, namely: (i) relativistic effects due to the travel of fast electrons close to planar interfaces while recording the spectrum, (ii) strain within GaN wells, and (iii) quantum confinement due to the width of the well reduction. The combination of these factors is found to contribute to the observed blue shift in plasmon energies for the strained GaN quantum wells. So the use of high-resolution valence electron imaging has offered the possibility to distinguish the interplay of different confined properties in strained GaN QWs, which is very promising for understanding and exploiting bandgap engineering of nowadays sophisticated devices.