Visible light-emitting diodes using a-plane GaN-InGaN multiple quantum wells over r-plane sapphire

We report blue-purple pn-junction light-emitting diodes (LEDs) with a-plane GaN-InGaN multiple quantum well active region. The LEDs were grown over r-plane sapphire substrates. Our study has shown the low pump intensity photoluminencence and electroluminescence to be dominated by emission from the band-tail states which then saturates rapidly giving rise to band-edge emission. (C) 2004 American Institute of Physics.