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

2015; Institute of Electrical and Electronics Engineers; Volume: 7; Issue: 3 Linguagem: Inglês

10.1109/jphot.2015.2430017

1943-0655

Pawan Mishra, Bilal Janjua, Tien Khee Ng, Chao Shen, A. Salhi, Ahmed Y. Alyamani, Munir M. El‐Desouki, Boon S. Ooi,

ZnO doping and properties

We investigated the design and growth of compositionally graded InGaN multiplequantum-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., In 0→x Ga 1→(1-x) N/In x Ga (1-x) N/In x→0 Ga (1-x)→1 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/cm2, respectively. The extended threshold current density rollover (droop) in graded-MQW-LED is due to the improvement in carrier uniformity and radiative recombination rate, which is consistent with the numerical simulation.