Photoluminescence Emission Efficiency Analysis Methodology by Integrating Raman Spectroscopy of the A₁(LO) and E₂(high) Phonons in a GaInN/GaN Heterostructure

Microscopic lattice vibration images of the E₂(high) mode (E₂^H) and another mode of A₁(LO) (A₁^L) or the higher energy branch of LO-phonon−plasmon coupling mode (LOPC+) in a Ga_0.95In_0.05N film on a GaN template are obtained by Raman scattering spectroscopy using a 325 nm laser. The increase in temperature by increasing the laser power is obtained from the decrease in the energy of E₂^H and the theoretical formula comprising two terms based on the mode energy variation of the bulk material and the thermal strain effect. Using the obtained temperature and the energy shift of the LOPC+, the mapping images of the temperature and electron density in the x–y plane are simultaneously obtained. This image provides the spatial variation of photoluminescence (PL) emission efficiency, given as PL intensity per electron. This method enables the quantitative discussion on photo-emission efficiency even in the regions of low or high carrier density affected by carrier transport. In the investigated area, a region with a lower PL efficiency is found despite a higher electron density and lower temperature increase than the surrounding region. This imaging analysis is feasible in integrating the carrier and thermal energy transports and recombination processes in carrier dynamics study.