GaN-based light emitting devices and crystal growth

Charge separation due to spontaneous and piezoelectric polarization inherent to the wurtzite structure has deleterious effects on the performance of most C-axis oriented devices. To overcome this problem, nonpolar GaN, such as A-plain and M-plain GaN substrates have been grown by using hydride vapor phase epitaxy (HVPE) at UCSB. Lateral epitaxial overgrowth (LEO) has been demonstrated to be an effective means of eliminating threading dislocations, basal plain stacking faults, and surface pits in A-plain GaN films. Blue LEDs were grown on nonpolar A-plain and M-plain GaN. The blue-shift of the peak emission wavelength with increasing the forward current was decreased dramatically. The turn-on voltage of the LEDs was relatively small. Roughened surface (RS) LEDs have been developed using photo enhanced chemical (PEC) etching. The sapphire substrate was removed by laser lift off