The heteroepitaxial growth of semipolar gallium nitride for light emitting diodes

The dramatic emergence of high brightness blue and green light emitting diodes (LEDs) and blue-violet laser diodes relies on the grown of GaN and related alloys along the polar [0001] direction of the wurtzite crystal structure. Discontinuities in the spontaneous and piezoelectric polarization fields at heterointerfaces in optoelectronic device structures lead to the formation of large internal electric fields (∼MV/cm), resulting in a red-shift in the emission wavelength, a decrease in the radiative recombination rate, and a blue-shift in the emission wavelength with increasing drive current. The QCSE may be minimized or eliminated through the growth of GaN orientations inclined with respect to the polar [0001] axis---these growth orientations have been termed semipolar GaN.; In this dissertation, metalorganic chemical vapor deposition has been employed for the heteroepitaxial growth of semipolar orientations of GaN. Substrate vicinality and growth conditions have been selected to optimized the growth of (1011) GaN on (100) spinel and (1122) GaN on (1100) sapphire. Semipolar LED structures have been demonstrated on both (10 11) and (1122) GaN orientations. The output power of the semipolar LEDs has been shown to depend primarily on the crystal quality of the semipolar template layers. A maximum output power of 89 muW at 20 mA was obtained for a heteroepitaxially grown (10 11) LED, while an output power of 394 muW at 20 mA and 6 mW at 350 mA was obtained for a homoepitaxially grown (10 11) LED. The surface of (1122) GaN was comprised of several facets, resulting in dual wavelength electroluminescence. Lateral epitaxial overgrowth (LEO) perpendicular to the GaN [11 23] stabilized the (1011) facets. A single emission peak at 452 nm was obtained for a semipolar LED structure structure grown on a (1122) LEO GaN template. The maximum output power obtained was 506 muW at 20 mA and 2 mW at 100 mA.