Analysis of stress-induced inhomogeneous electroluminescence in GaN-based green LEDs grown on mesh-patterned Si(111)substrates with n-type AlGaN layer

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.