Ultrafast Carrier Dynamics Of Conformally Grown Semi-Polar (1122) Gan/Ingan Multiple Quantum Well Co-Axial Nanowires On M-Axial Gan Core Nanowires

The growth of semi-polar (112 2) GaN/ InGaN multiple-quantum-well (MQW) co-axial heterostructure shells around m-axial GaN core nanowires on a Si substrate using MOCVD is reported for the first time. The core GaN nanowire and GaN/ InGaN MQW shells are grown in a two-step growth sequence of vapor-liquid-solid and vapor-solid growth modes. The luminescence and carrier dynamics of GaN/ InGaN MQW coaxial nanowires are studied by photoluminescence, cathodoluminescence, and low temperature time-resolved photoluminescence (TRPL). The emission is tuned from 430 nm to 590 nm by increasing the InGaN QW thickness. The non-single exponential decay measured by low-temperature TRPL was attributed to the indium fluctuations in the InGaN QW. The ultrafast radiative lifetime was measured from 14 ps to 26 ps with different emission wavelengths at a very high internal quantum efficiency up to 68%. An ultrafast carrier lifetime was assigned to the growth of the InGaN QW on semipolar (112 2) growth facet and the improved carrier collection efficiency due to the radial growth of the GaN/ InGaN MQW shells. Such an ultrafast carrier dynamics of NWs provides a meaningful active medium for high speed optoelectronic applications.