Achieving Uniform Carrier Distribution in MBE-Grown Compositionally Graded InGaN Multiple-Quantum-Well LEDs

作者：Mishra, Pawan; Janjua, Bilal; Ng, Tien Khee; Shen, Chao; Salhi, Abdelmajid; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.^*

来源：IEEE Photonics Journal, 2015, 7(3): 2300209.

DOI：10.1109/JPHOT.2015.2430017

• Compositional grading
• light-emitting diodes (LEDs)
• polarization field
• semiconductor quantum well
• solid-state lighting
• wavefunction overlap

We investigated the design and growth of compositionally graded InGaN multiple-quantum-well (MQW)-based light-emitting diodes (LEDs) without an electron-blocking layer. Numerical investigation showed uniform carrier distribution in the active region and higher radiative recombination rate for the optimized graded-MQW design, i.e., In0 -> xGa1 ->(1-x)N/InxGa(1-x)N/Inx -> 0Ga(1-x)-> N , as compared with the conventional stepped-MQW-LED. The composition-grading schemes, such as linear, parabolic, and Fermi-function profiles, were numerically investigated for comparison. The stepped-and graded-MQW-LEDs were then grown using plasma-assisted molecular beam epitaxy through surface-stoichiometry optimization based on reflection high-energy electron diffraction in situ observations. Stepped-and graded-MQW-LED showed efficiency roll over at 160 and 275 A/cm(2), respectively. The extended threshold current density roll-over (droop) in graded-MQW-LED is due to the improvement in carrier uniformity and radiative recombination rate, which is consistent with the numerical simulation.

• 出版日期2015-6