Photoluminescence and electroluminescence properties of GaN-based LED chips with defective regions at low excitation levels

Defective regions of LED epi-wafers and chip-wafers could be observed by a photoluminescence (PL) imaging method. As the defective regions contain high density nonradiative recombination centers, the LED chips with defective regions showed different optical properties from those of LEDs with no defective regions found by PL imaging. At low optical excitation power levels, the PL properties were influenced by nonradiative recombination dominantly. Similar phenomena were observed from electroluminescence (EL) properties at low electrical excitation levels. Research results on the similarity and difference between PL and EL properties of LED chips are presented.