Excitonic properties of polar, semipolar, and nonpolar InGaN/GaN strained quantum wells with potential fluctuations

Abstract

Excitonic properties of polar, semipolar, and nonpolar InGaN/GaN strained quantum wells (QWs) were investigated in terms of exciton localization and polarization-induced electric fields. The spontaneous emission lifetimes measured at ~10 K for the (0001) polar QWs were 1.4 ns at an emission wavelength of 400 nm, but increased monotonically to 85 ns at 520 nm. On the other hand, those for {11[overline 2]2} and {1[overline 1]01} semipolar QWs and {11[overline 2]0} and {1[overline 1]00} nonpolar QWs were on the order of a few hundred picoseconds and independent of the emission wavelength. To quantitatively discuss these results, the crystalline orientation dependence of the spontaneous emission lifetime of 1s heavy hole excitons in InGaN/GaN QWs at 0 K was calculated, when lateral confinements were considered to express well-reported potential fluctuations. It is revealed that both the crystalline orientation and lateral confinement vary the spontaneous emission lifetime by orders of magnitude. Analyses of the experimental results suggest that excitons in the (0001) polar QWs are more strongly localized as the In composition increases, but the semipolar and nonpolar QWs exhibit the opposite tendency. These tendencies are attributed to differences in the growth characteristics.