Characterization of internal quantum efficiency of InGaN-based green LEDs grown on Si with various buffer strain.

This work presents a characterization study on the internal quantum efficiency of InGaN-based green light-emitting diodes (LEDs) grown on Si with a markedly different buffer strain. One with a huge residual compressive strain but a low density of threading dislocations (TDD, ∼9.0 × 10cm) by using the conventional Al-composition step-graded AlN/AlGaN buffer, and the other nearly strain-free but with a relatively high TDD (∼2.5 × 10cm) by using an AlN single-layer buffer. An intriguing difference in internal quantum efficiency of 56% and 78% for the two samples is revealed. By combining temperature-dependent and time-resolved photoluminescence studies to modify the classical Arrhenius formula, it is evident that the strain relaxation of multiple quantum wells can generate a substantial amount of defects. Moreover, the radiative and non-radiative recombination efficiency as a function of excitation power is extracted according to the ABC model by performing the power-dependent photoluminescence characterization. Finally, a possible model for the carrier recombination dynamics of the InGaN-based green LEDs grown on Si under a low (below 100 µW, < 10cm) to high excitation (above 10 mW,>10cm) is proposed.