UC Santa Barbara

This dissertation presents measurements of the photocurrent in forward biased III-Nitride light emitting diodes (LEDs). This photocurrent is observed to be in the forward direction, and is therefore attributed to the hot carriers being generated by Auger recombination in the active region of the device. There is strong evidence that Auger recombination is the cause of the well-known phenomenon of efficiency droop in III-Nitride LEDs, which significantly limits the efficiency of high brightness LED lighting. Therefore, the photocurrent measurements presented in this dissertation are a step towards a benchtop technique to more easily study the physical origins of efficiency droop in commercial LEDs.

First, single quantum well (SQW) devices are studied, as these are the simplest platform to interpret the results of the measurements. Next, devices with multiple quantum wells (MQW) are studied, as all commercial LEDs are MQW devices. Additionally, measurements of LEDs grown by ammonia molecular beam epitaxy (NH3 MBE) are presented. These LEDs show no droop, even out to high drive current densities. Finally, measurements of the photocurrent in LEDs processed from commercial epi are presented.