In this dissertation, we use a combination of simulations and experimental work to study the physics and material properties of nonpolar/semipolar InGaN quantum wells (QWs). Comprehensive studies on epitaxial growths, fabrication technologies as well as device characterizations were carried out to identity and overcome the major challenges for the realizing of high performance blue and green light-emitting diodes (LEDs).

The performance of InGaN LEDs is several limited by the combined effects of high indium compositions and polarization-related fields. To minimize these effects, the indium incorporation properties on various nonpolar/semipolar devices were studied by electroluminescence (EL) characterization and x-ray diffraction (XRD) analysis. In addition, the defect formation mechanisms for high-indium-content QWs as well as the corresponding suppression strategies were also explored for the growth of the high efficiency defect-free semipolar LEDs.

The low light extraction (&eegr;extr) was another long-term limiting factor for the efficiency of semipolar/nonpolar LEDs. To circumvent this problem, we show that advanced fabrication techniques of surface patterning with conical features can effectively improve the &eegr;extr and corresponding emission power for semipolar/nonpolar LEDs. Feature pitch, size, and depth were varied to optimize the extraction efficiency. The experimental results were confirmed by the ray tracing simulations.

One important feature of semipolar/ nonpolar QWs is polarized spontaneous emission due to the broken symmetry and associated valance band splitting. The optical polarization properties were studied on selective semipolar InGaN LEDs by EL measurement and theoretical calculations (k•p method). Strain and the QWs composition profiles strongly affect the polarization properties.

By engineering these unique properties, semipolar blue and green LEDs with state-of-the-art performance were achieved. We demonstrate the world's first semipolar blue LEDs with over 50% EQE and first semipolar green LEDs with 30% EQE. We further demonstrate that high emission power (266.5 mW) and high efficiency (45.3%) under high current densities (> 200A/cm2) (i.e., the "low droop" operation) can be achieved on these small size (0.1 mm2) semipolar devices. These results prove that semipolar LEDs have the potential to revolutionize the lighting applications with energy efficient and cost effective solutions.