Reducing a Piezoelectric Field in InGaN Active Layers by Varying Pattern Sapphire Substrates

Internal quantum efficiency (IQE) and piezoelectric field (PZ) in InGaN light-emitting diodes (LEDs) were analyzed that were grown on a truncated pyramid (TP)- and a pyramid (P)-shaped pattern sapphire substrates. Lower flat-band voltage was measured at -8 V in the P-LED compared with the TP-LED (-12 V) that showed a low PZ was observed in the P-LED structure. The IQE value of the P-LED was measured as 86%, which is higher than that of the TP-LED (76%). High IQE, low PZ, and high light extraction efficiency were observed in the InGaN LED structure grown on the P-shaped pattern sapphire substrate.