On-Chip 3d Confocal Optical Study Of An Ingan/Gan Microrod Led In The Low Excitation Regime

In this work, we studied p-i-n InGaN/GaN core-shell microrod (mu rod) LEDs using confocal microscopy with a spatial resolution below 500 nm in all three dimensions. At low excitation conditions, the devices emit in the red spectral range, while green and blue emissions become more prominent with increasing driving current. 3D photoluminescence (PL) maps demonstrate that the red emission originates from the apex of the tip area, while the green emission stems from the corners between m- and r-planes and the dominant blue emission from the m-plane. Analyzing individual mu rods of the LED chip in a closed circuit configuration, a pronounced photocurrent is found for quasi-resonant laser excitation, indicating charge carrier tunneling losses out of the quantum well. This hypothesis is confirmed by applying an external voltage in the forward direction, where a characteristic blueshift of the single mu rod PL signal is observed due to a modified band alignment, and a nonlinear increase in the PL intensity proves suppressed tunneling losses.