Investigation On The Wide Spectrum Nano-Folding Of Active Region LED Technology

As GaN based Light Emitting Diode (LED) has been more and more commercially available, the efficiency enhancement of LED is still an important problem for its further application. In this thesis, GaN based material and device structure were grown by Thomas Swan 3 2"metal organic chemical vapor deposition (MOCVD) systems. The material growth conditions and the optimized LED growth parameters were investigated, which were applied to the growth of GaN based nano-LED structure to improve the efficiency of nano-LED.The effects of growth temperature, In/Ga molar ratio, V/III ratio, and reactor pressure on the heteroepitaxial growth of InGaN films on GaN/sapphire template were studied by means of in-situ monitoring system and high-resolution X-ray diffraction (HRXRD). The results show that, a lower growth temperature, relatively high In/Ga molar ratio, a lower V/III ratio and higher reactor pressure would lead to a higher In content of InGaN films. In addition, higher reactor pressure helps improving the crystalline quality of InGaN epilayer.Exploring Hall, atomic microscopy (AFM) and electroluminescence (EL) measurements, the influences of Cp2Mg/TMGa molar ratio, growth temperature and V/III ratio on the carrier concentration of p-typed GaN were studied. The effect of growth rate on the growth of p-typed GaN was also examined. It is found that the hole concentration was reduced by excessively high Cp2Mg/TMGa molar ratio, high growth temperature, and great V/III ratio. An excessively growth rate would lead to a lower crystalline quality of p-typed GaN epilayer.LED structure was grown with optimized growth conditions on GaN nanorod arrays which were fabricated by dry-etching with self-assembled Ni clusters as mask. The PL integrated intensity of LED structure grown on nanorods template is about 2 times stronger compared with that grown on conventional GaN substrate. And the FWHM of PL spectra is also decreased for nano-LED. The device grown on GaN nanorods template showed excellent rectifying behavior with a forward voltage of 4.6V under 20 mA, a leakage current of 10μA under -5V. The value of ideal factor n is about 10.5.