Recombination dynamics of localized excitons in cubic In_xGa_(1-x)N/GaN multiple quantum wells grown by radio frequency molecular beam epitaxy on 3C-SiC substrate

摘要

Recombination dynamics of localized excitons in strained cubic (c-)In_xGa_(1-x)N/GaN multiple quantum wells (MQWs) grown on 3C-SiC (001) were summarized in terms of well thickness L, InN molar fraction x, and temperature T. Photoluminescence (PL) peak energy of c-In_(0.1)Ga_(0.9)N/GaN MQWs showed a moderate blueshift as L decreased, and the low-temperature PL lifetime did not change remarkably by changing L. These results proved that the quantum-confined Stark effect due either to spontaneous or piezoelectric polarization was inactive in cubic polytypes. Consequently, time-resolved PL (TRPL) data of c-InGaN MQWs reflect the intrinsic exciton dynamics. The TRPL signal showed stretched exponential decay and spectral redshift with time after excitation up to 300 K. The results are fingerprints that the spontaneous emission is due to the radiative recombination of excitons localized in disordered quantum nanostructures forming extended and localized states. Effective localization depth increased with the increase in x, which gave rise to fast exciton localization. However, nonradiative lifetime in the free or extended states decreased more rapidly with the increase in x and T, giving the emission efficiency maximum at particular x around 0.1.