Origin of high quantum efficiency in Si-based homoepitaxial InGaN/GaN light-emitting diodes

Si-based optical devices would benefit significantly from large scalable and economic illumination sources. Although we previously demonstrated Si-based homoepitaxial light-emitting diodes (LEDs) with large scalability and highly efficient opto-electrical characteristics, the origin of their high quantum efficiency has not been explored. Here, we reveal the origin of the significantly improved quantum efficiency of InGaN/GaN blue LEDs on Si-based freestanding GaN. In power-dependent photoluminescence measurements, the redshifts and blueshifts with increasing injection power indicate a reduced internal electric field of the devices. Furthermore, time-resolved photoluminescence curves for the Si-based homoepitaxial InGaN/GaN LEDs exhibit much larger decay components, suggesting a reduced piezoelectric polarization field, strong quantum confinement effect, and improved material quality of the LEDs. A relatively improved external quantum efficiency of the diodes also confirms the reduced dislocation density and internal electric field in the homoepitaxial device. These findings clearly support that the suppressed structural defects and piezoelectric polarization field are responsible for the remarkable quantum efficiency of the InGaN/GaN blue LEDs on Si-based freestanding GaN.