Studies of InGaN/GaN multiquantum-well green-light-emitting diodes grown by metalorganic chemical vapor deposition

InGaN(3 nm)/GaN(5 nm) three period multiquantum green-light-emitting diodes (LEDs) grown by the metalorganic chemical vapor deposition technique have been studied using high-resolution transmission electron microscopy (HRTEM), double crystal high resolution x-ray diffraction (HRXRD) and low temperature photoluminescence. HRTEM analysis showed that the defect density gradually decreased in the growth direction with increasing thickness. Self-assembled quantum dot-like structures in the wells and black lumps between the well and barrier due to In segregation and strain contrast were observed, respectively. The HRXRD spectrum of the green LED structure was simulated using the kinematical theory method to obtain the composition and thickness of the well and barrier. The quantum-well (QW) green emission peak 2.557 eV at 10 K showed "S" shaped shift like a red-blue-red shift with variation of the temperature in the photoluminescence spectra due to potential fluctuations caused by inhomogeneous alloy distribution in the wells. The activation energy of 49 meV obtained from the QW green emission line indicated deepening of the localization of the carriers. (C) 2004 American Institute of Physics.