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

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.

Effects of electrical stress on the characteristics and defect behaviors in GaN-based near-ultraviolet light emitting diodes

“…For GaN-based LEDs, it is suggested that electrical stress-induced degradation can be attributed to the generation or the propagation of point defects activated by carrier transport, such as vacancies or anti-site defects. [8][9][10][11][12] In addition, effects of dislocations on device degradation cannot be ignored for NUV LEDs [13][14][15] due to the lack of In-rich clusters that separate carriers from dislocations. [16] However, the behavior of defects that cause device degradation has yet to be confirmed.…”