Luminescence and lasing in GaN epitaxial layers and InGaN/GaN quantum well heterostructures under optical and electron-beam excitation

Interrelation between stimulated and excitonic emission intensity of GaN epitaxial layers and yellow luminescence intensity as well as correlation between photoluminescence and laser properties of InGaN based multiple quantum well heterostructures was investigated. It was found among all studied undoped GaN epitaxial layers that the higher intensity of the yellow luminescence and so the higher concentration of the yellow luminescence related centres the higher is the excitonic, electron–hole plasma and stimulated emission intensity. It was shown that a small Stokes shift and a high ratio of the luminescence intensity from InGaN quantum well layers to the photoluminescence intensity from GaN barrier layers indicate high laser quality of the multiple quantum well heterostructures. The lowest full width at half maximum of the laser line was 0.04 nm, the highest operating temperature was 585 K, the lowest threshold was 100 kW cm−2, the highest characteristic temperature was 164 K and the highest wavelength was 442.5 nm. The far-field patterns of the laser emission from the MQW lasers consist of two approximately symmetrical high brightness spots localized at angles α=±30–35°.