Recombination Rate Analysis of InGaN-Based Red-Emitting Light-Emitting Diodes
Haotian Xue, Syed Ahmed Al Muyeed, Elia Palmese, Daniel Rogers, Renbo Song, Nelson Tansu, Jonathan J. Wierer
Abstract
The recombination rates are measured and analyzed for red-emitting InGaN light-emitting diodes (LEDs) to better understand the factors that limit their efficiency. InGaN/AlGaN/GaN multiple quantum well (MQWs) are grown with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{x}\ge 0.28$ </tex-math></inline-formula> in the InxGa <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1-x}}\text{N}$ </tex-math></inline-formula> quantum well. The AlyGa <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1-y}}\text{N}$ </tex-math></inline-formula> interlayers (ILs) with high Al-content ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{y}>$ </tex-math></inline-formula> 0.8) are employed because they result in smoother surfaces with smaller V-pits and higher photoluminescence efficiency. The IL-MQWs are formed on GaN and InzGa <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1-z}}\text{N}$ </tex-math></inline-formula> /GaN superlattice (SL) underlayers (ULs) with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z =0.015$ </tex-math></inline-formula> , 0.025, and 0.065. Differences in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula> coefficients (radiative recombination) within this set result from changes in wavefunction overlap caused by differences in layer thickness and composition in the IL-MQW. IL-MQWs grown on SL-ULs have <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$A$ </tex-math></inline-formula> coefficients (Shockley-Reed-Hall recombination) that are lower than expected, indicating that the SL-ULs help reduce defect formation. Compared to shorter wavelength InGaN-based LEDs, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B$ </tex-math></inline-formula> coefficients are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim $ </tex-math></inline-formula> 100 times lower due to lower wavefunction overlap. A and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> coefficients are higher because of a higher number of defects.