Enhanced microLED efficiency via strategic pGaN contact geometries
Keith Behrman, Ioannis Kymissis
Abstract
Micro light-emitting diode (microLED) structures were modeled and validated with fabricated devices to investigate p-type GaN (pGaN) contact size dependence on power output efficiency. Two schemes were investigated: a constant 10 μm diameter pGaN contact and varying microLED sizes and a constant 10 μm diameter microLED with varying contact sizes. Modeled devices show a 17% improvement in output power by increasing the microLED die size. Fabricated devices followed the same trend with a 70% improvement in power output. Modeled microLED devices of a constant size and varying inner contact sizes show optimized power output at different current densities for various contact sizes. In particular, lower current densities show optimized output for smaller pGaN contacts and trend towards larger contacts for higher current densities in a balance between undesirable efficiency losses at high-current injection and preventing surface recombination losses. We show that for all device geometries, it is preferential to shrink the pGaN contact to maximize efficiency by suppressing surface recombination losses and further improvements should be carefully considered to optimize efficiency for a desired operational brightness.