Radiative and nonradiative lifetimes in nonpolar m-plane InxGa1−xN∕GaN multiple quantum wells grown on GaN templates prepared by lateral epitaxial overgrowth

Abstract

Different from the case for polar (0001) InxGa1−xN multiple quantum wells (MQWs), the effective radiative lifetimes (τR,eff) at 8K of violet (V: 3.15eV), purple (P: 3.00eV), and blue (B: 2.83eV) emission peaks in nonpolar (11¯00) InxGa1−xN∕GaN MQWs fabricated on various GaN templates were found to be nearly independent of InN molar fraction x being approximately 1ns. The result indicates the absence of polarization fields parallel to the MQW normal. For each luminescence peak, the effective nonradiative lifetime (τNR,eff) at room temperature of the MQWs grown on “Ga-polar” wings of the GaN template prepared by lateral epitaxial overgrowth (LEO) was longer than that for the MQWs grown on “N-polar” wings, windows, or on conventional GaN templates, which had high density basal plane stacking faults and threading dislocations. Since τR,eff was little affected by the presence of defects, the increase in τNR,eff brought fivefold improvement in the equivalent internal quantum efficiency (ηinteq) of V peak. Because B peak was mostly generated from defective areas, the increase in ηinteq was not so remarkable (29%–36%). However, these values are approximately twice that reported for (112¯0) InGaN∕GaN MQWs grown on LEO GaN templates [Onuma et al., Appl. Phys. Lett. 86, 151918 (2005)].