High-resolution nonlinear optical spectroscopy of InGaN quantum dots in GaN nanowires

Using frequency-domain nonlinear spectroscopy methods, we find relatively broad (∼20–30  meV) resonances from quantum confined electron–hole pairs in an ensemble of InGaN disks in GaN nanowires that persist without significant broadening up to room temperature in the nonlinear absorption spectrum. Under these growth conditions, we find that the kinetics related to the nonlinear signal are dominated by metastable traps with decay rates of microseconds at low temperatures, as evidenced in part by high-frequency-resolution scans within the broad absorption resonances. The data reveal ultranarrow population pulsation resonances with linewidths that indicate the slow decay rate of the metastable traps.