Distinct temperature-dependent dynamic behaviors of GaN-based blue light-emitting diodes (LEDs) are observed by use of the very-fast electrical-optical pump-probe technique. Our static and impulse response measurement results indicate that the behaviors of internal carrier dynamics under different ambient temperatures can be classified into three regimes covering a wide range of bias current densities (20-2000 A/cm 2). The first regime is when the bias current density ranges from low to moderate (20-100 A/cm 2 ). The measured external quantum efficiency (EQE) degrades dramatically from 57 to 44%, and the measured waveform and extracted time constants of measured impulse responses are invariable from room temperature (RT) to 200 °C, which indicates that the carrier leakage is not an issue for the observed droop phenomenon. When the bias current density further increases to near 1 kA/cm 2, the droop phenomenon are mitigated (44 to 24%). However, a significant shortening of the measured impulse response happens under 200 °C operation due to the device-heating effect. This phenomenon is diminished when the bias current densities are further increased to over 1 kA/cm 2, due to the screening of the piezoelectric field. The extracted time constants can also be used to explain the droop phenomenon in GaN LED under high bias currents.
All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering