Structural, electrical, and optical characterizations of a-plane InGaN/GaN quantum well structures

GaN and related ternary compounds have been widely used for fabrication of light emitting diodes (LEDs) and laser diodes (LDs). Especially, the low-dimensional systems such as quantum wells (QWs), quantum wires, and quantum dots have been investigated as an effective structure for improving the efficiency of light-emitting devices such as light emitting diodes and laser diodes. Generally, the quantum well active regions in I¿-nitride optoelectronic devices grown on conventional templates along the polar orientation have critical problems given by the quantum confined Stark effect (QCSE) due to the effects of strong piezoelectric and spontaneous polarizations. However, the QWs grown on nonpolar templates along aor m-directions are free from the QCSE since the polar-axis lies within the growth plane of the template. In this study, we achieved high quality a-plane GaN films on sapphire substrates and characterized structural, electrical and optical properties in the a-plane InGaN/GaN QW structures. High quality of a-plane GaN templates was confirmed by using selected area diffraction (SAD) patterns and high resolution x-ray diffraction (HRXRD) results. To investigate the electrical properties of aplane GaN QWs structures, the temperature-dependent carrier depth profiles which can determine the carrier confinement with nanoscale spatial resolution were studied. And the redshift of photoluminescence (PL) peaks with increasing temperature will be intensively discussed.