Analysis of stress-induced inhomogeneous electroluminescence in GaN-based green LEDs grown on mesh-patterned Si (111) substrates with n-type AlGaN layer**Project supported by the National Key Research and Development Program of China (Grant Nos. 2017YFB0403105 and 2017YFB0403100) and the National Natural Science Foundation of China (Grant Nos. 11674147, 61604066, 51602141, and 11604137).

Abstract

Inhomogeneous electroluminescence (EL) of InGaN green LEDs grown on mesh-patterned Si (111) substrate had been investigated. Sample with n-AlGaN inserted between the pre-strained layers and the first quantum well showed the inhomogeneous EL in the low current density range. Near-field EL emission intensity distribution images depicted that inhomogeneity in the form of premature turn-on at the periphery of the LED chip, results in stronger emission intensity at the edges. This premature turn-on effect significantly reduces the luminous efficacy and higher ideality factor value due to locally current crowding effect. Raman measurement and fluorescence microscopy results indicated that the partially relaxed in-plane stress at the edge of the window region acts as a parasitic diode with a smaller energy band gap, which is a source of edge emission. Numerical simulations showd that the tilted triangular n-AlGaN functions like a forward-biased Schottky diode, which not only impedes carrier transport, but also contributes a certain ideality factor.