Investigation of Strained Multi-Quantum Well Structures for High Bright AlGaInP-Based Light Emitting Diodes

We have investigated the effects of well strain on optical and device characteristics of AlGaInP-based multi-quantum well (MQW) light-emitting diodes (LEDs) according to the variation of well strain and the corresponding change of well thickness in order to maintain the operating wavelengths. As the compressive well strain increased from +0.04 to +0.41% and the corresponding well thickness decreased from 7.2 to 4.5 nm, the relative photoluminescence (PL) intensity increased from 1.0 to 1.21, and the radiative carrier lifetime measured from the time-resolved PL (TRPL) was shortened from 4.43 to 1.77 ns. The compressive well strain may cause the strain-induced heavy-hole-assisted recombination process, followed by reduction of the radiative decay time due to a reduced effective-heavy-hole mass. In addition, a thinner well thickness may enhance the spatial carrier confinement in the well regions, which greatly improved light output power of the LEDs. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/JJAP.48.072204