Edge‐Emitting Photoluminescence/Electroluminescence Polarization Studies of InGaN/GaN Structures Grown by MOCVD on (0001) Sapphire

Abstract

This paper compares results from different sets of typical blue/green InGaN/GaN structures (MQWs, LEDs) grown in EMCORE's commercial reactors (EMCORE GaNzilla and SpectraGaN) on (0001) sapphire. Edge-emitting photoluminescence (PL) and electroluminescence (EL) were used to characterize representative samples from each set. The PL/EL state of polarization was investigated and compared to theoretical evaluations. Blue (∼475 nm) structures exhibit strongest polarizations, up to a 3:1 TE to TM ratio. Green (∼520 nm) structures exhibit smaller polarizations, about a 1.5:1 ratio. Polarization of luminescence in edge geometry also enables a clear distinction between quantum well (QW) and quantum dot (QD) cases in supperlattice structures. For the blue samples a QW-like behavior is observed since the TE mode dominates the TM mode 3:1. In contrast, for the green samples a mixed QW-QD behavior is suggested, as the TE:TM ratio drops to 1.5:1. PL/EL polarization fringes were also observed and a possible correlation with interfaces quality suggested. The implications of these results for high power optoelectronic and electronic devices will be addressed.