InGaN-based greenish separate confinement heterostructures

For opto-electronic applications green laser diodes (LDs) are of great interest. The fabrication of such GaN-based light emitting diodes (LEDs) and LDs however faced different problems ranging from the lack of adequate homoepitaxial substrates to the miscibility gap of InGaN. Recently there have been reports of laser diodes based on InGaN quantum wells (QWs) in the green spectral region. In this work the influence of InGaN quantum dots (QDs) on the opto-electronic properties of LDs is discussed in detail. All samples were grown by metal-organic vapour-phase epitaxy on free-standing GaN substrates from Lumilog and the number of QD stacks or QWs was varied. The samples were processed as ridge and deep ridge waveguide structures with different ridge widths and measured by high-resolution X-ray diffraction and electroluminescence, and light-current (L-I) and current-voltage (I-V) characteristics were recorded. A comparison of all different growths and process designs in respect of opto-electronic properties is presented.