Strain engineering for the solution of efficiency droop in InGaN/GaN light-emitting diodes

Department of Materials Science and Engineering, Division of Advanced Materials Science,Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Korea.
Optics Express (Impact Factor: 3.49). 03/2010; 18(6):5466-71. DOI: 10.1364/OE.18.005466
Source: PubMed


We present a method of increasing light output power and suppressing efficiency droop in vertical-structure InGaN/GaN MQW LEDs without modifying their epitaxial layers. These improvements are achieved by reducing the quantum-confined Stark effect (QCSE) by reducing piezoelectric polarization that results from compressive stress in the GaN epilayer. This compressive stress is relaxed due to the external stress induced by an electro-plated Ni metal substrate. In simulations, the severe band bending in the InGaN quantum well is reduced and subsequently internal quantum efficiency increases as the piezoelectric polarization is reduced.

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