Effect of growth pressure of undoped GaN layer on the ESD characteristics of GaN-based LEDs grown on patterned sapphire

The effect of growth pressure of underlying undoped GaN(u-GaN) layer on the electrical properties of GaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSS) is evaluated. The electrostatic discharge (ESD) endurance voltages could increase from 4000 to 7000 V when the growth pressure of u-GaN layers is increased from 100 to 500 torr, while the forward voltages and light output powers remain almost the same. Poor ESD endurance ability could be attributed to the underlying GaN layer grown under relative low pressure, which leads to significant surface pits. This could be further attributed to the imperfect coalescence of crystal planes above the convex sapphire patterns. The pits are associated with TDs behaving as a leakage path to degrade electrical performance.