Radiative and nonradiative lifetimes in nonpolar m-plane In_xGa_1-xN/GaN multiple quantum wells grown on GaN templates prepared by lateral epitaxial overgrowth

Different from the case for polar (0001) In_xGa_1-xN multiple quantum wells (MQWs), the effective radiative lifetimes (τ_R,eff) at 8 K of violet (V: 3.15 eV), purple (P: 3.00 eV), and blue (B: 2.83 eV) emission peaks in nonpolar (1100) In_xGa_1-xN/GaN MQWs fabricated on various GaN templates were found to be nearly independent of InN molar fraction x being approximately 1 ns. The result indicates the absence of polarization fields parallel to the MQW normal. For each luminescence peak, the effective nonradiative lifetime (τ_NR,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 τ_R,eff was little affected by the presence of defects, the increase in τ_NR,eff brought fivefold improvement in the equivalent internal quantum efficiency (η_int^eq) of V peak. Because B peak was mostly generated from defective areas, the increase in η_int^{- - eq} was not so remarkable (29%–36%). However, these values are approximately twice that reported for (1120) InGaN/GaN MQWs grown on LEO GaN templates [Onuma etal, Appl. Phys. Lett. 86, 151918 (2005)].