Growth of a-axial GaN core nanowires, semi-polar ([formula omitted]) GaN/InGaN multiple quantum well co-axial nanowires on Si substrate, and their carrier dynamics

Abstract

The quantum-confined Stark effect (QCSE) reduces the quantum efficiency of optical devices due to the reduced overlap of electron and hole wave functions because of the growth of GaN/InGaN multiple quantum wells (MQWs) on the polar facet. Here, we report the growth of non-polar [112‾0] GaN core nanowires on Si substrate by MOCVD. Subsequently, the active region of GaN/InGaN MQWs is grown on (11‾01) semipolar growth facet. The morphology of GaN core and GaN/InGaN MQWs is examined by SEM and TEM. The growth direction of GaN core and GaN/InGaN MQWs is confirmed by SAED patterns. The bandgap is tuned from 3.11 eV to 2.45 eV by increasing the InGaN QW thickness. Finally, time-resolved photoluminescence is conducted to evaluate the carrier dynamics. An ultrashort time constant between 51 ps and 74 ps is measured with increased QW thickness. The underlying reason for the very short carrier lifetime is the suppressed QCSE because the piezoelectric and polarization fields are reduced due to the semi-polar growth facet of QWs. The semi-polar growth of GaN/InGaN MQW co-axial nanowires on Si substrate underlines the potential of our fabrication technique for a variety of optical applications.