STRUCTURAL ORIGIN OF V-DEFECTS AND CORRELATION WITH LOCALIZED EXCITONIC CENTERS IN INGAN GAN MULTIPLE-QUANTUM WELLS/

In the growth of InGaN/GaN multiple quantum well (MQW) structures, a n ovel defect (called the ''V-defect'') initiates at threading dislocati ons in one of the first quantum wells in a MQW stack. This defect is c ommon to almost all InGaN MQW heterostructures. The nature of the V-de fect was evaluated using transmission electron microscopy (TEM), scann ing TEM (STEM), and low-temperature cathodoluminescence (CL) on a seri es of In0.20Ga0.80N/GaN MQW samples. The structure of the V-defect inc ludes buried side-wall quantum wells (on the {<10(1)over bar 1>} plane s) and an open hexagonal inverted pyramid which is defined by the six {<10(1)over bar 1>} planes. Thus, in cross section this defect appears as an open ''V''. The formation of the V-defect is kinetically contro lled by reduced Ga incorporation on the pyramid walls ({<10(1)over bar 1>} planes). The V-defect is correlated with the localized excitonic recombination centers that give rise to a long-wavelength shoulder in photoluminescence (PL) and CL spectra. This long-wavelength shoulder h as the following characteristics: (i) its intensity is correlated with the side-wall quantum wells; (ii) the temperature independence of the full width at half maximum strongly supports a localized exciton reco mbination process. (C) 1998 American Institute of Physics.