Light output improvement of InGaN ultraviolet light-emitting diodes by using wet-etched stripe-patterned sapphire substrates

GaN-based epilayers are grown on wet-etched stripe-patterned sapphire substrates, with stripes along the ⟨11−20⟩sapphire and ⟨1−100⟩sapphire directions, for 400nm ultraviolet light-emitting diodes (LEDs). The effects of the etching depth and stripe orientation on the structural and optical properties of the GaN layer as well as on the LEDs are investigated. Much better material quality and light output power are obtained when the GaN and the LEDs are grown on a 0.9μm deep patterned sapphire substrate with stripes along the ⟨1−100⟩sapphire direction. Stripe-orientation dependent growth modes accounting for the observed experimental results are proposed.