Opto-electronic devices based on wurtzite group-III nitride films with non-polar orientations

Group-III nitride semiconductors, which have stable wurtzite crystal structure, are today amongst the most important materials for opto-electronic device applications. Currently all commercially available nitride light emitting devices are made with C-plane oriented films, where growth is along the c-axis . However large piezo-electric and pyro-electric effects in these materials lead to high interfacial charge density and electric fields in heterostructure quantum wells having C-plane orientation. The high electric field (~ MV/cm) is detrimental for light emitting devices which generally have a quantum well in the active region. It spatially separates electrons and holes within the well, thereby reducing the radiative lifetime and consequently the efficiency of the device. A way to overcome this problem is by the use of films with non-polar orientations, whose normal to the surface is perpendicular to the c-axis, such as M-plane and A -plane films.