The Fabrication And Optical Properity Of GaN Nanorod

GaN is a new type of semiconductor material for microelectronic devices, optoelectronic devices, and together with SiC, diamond and other semiconductor materials, known as the third generation of semiconductor materials,and Ge, Si is the first generation of semiconductor materials, the second generation of GaAs, InP compound semiconductor material. It has a wide direct bandgap, strong bond, high thermal conductivity, good chemical stability properties and strong anti-radiation ability, has a wide application in optoelectronics, high-temperature and high-power devices and high frequency microwave device applications. Nanostructures have many advantages:on the one hand, nanorod structures may relieve strain and thus accommodate the large lattice mismatch at hetero-interface, so the radiative recombination efficiency and the internal quantum efficiency of the LED device can be enhanced, on the other hand, because of the large sidewall surface of nanorods, light extract efficiency can also be improved. In addition, the inclined threading dislocations may cease in the nanorod’s side surface and decrease dislocation density, which can reduce the nonradiative recombination efficiency and thus improves the device performance significantly. Due to the great advantages of the nanostructures over the bulk material, they have been used in super-bright LEDs, full colour displays, etc. There are several methods to fabricate GaN nanorods, generally it’s classified into two methods:top-down and down-top approach. The down-top approach is a self-organized growth technique, it includes many methods, such as catalyst assisted Vapor-Liquid-Solid (VLS) growth, catalyst free or self-induced growth and selective area growth on nano-patterned substrate. While top-down approach includes methods like conventional photolithography, e-beam lithography, self-organized nanomasking or nanosphere lithography.In this paper, GaN nanorods were fabricated by ICP using Ni self-assembled nanodots as etching mask, the morphology was checked by scanning electron microscopy (SEM) and the optical property was characterized by the photoluminescence (PL) spectra at room temperature. The results are listed here:1. As the RF power and ICP power increased, the etch rate increased, this was due to the enhanced physical bombardment and ion density, but the PL intensity of GaN nanorods didn’t change linearly with the change of RF and ICP power.2. The PL intensity of GaN nanorods was enhanced about 2.6 times compared to that of as-grown GaN films, we also measured the Raman of GaN film and GaN nanorod, compared with the GaN film, the stress relaxion was found in GaN nanorod.3. Further chemical treatment was applied to the sample in order to heal the etch damage. The GaN nanorods were dipped into the KOH solution for 45 minutes. The photoluminescence (PL) spectra was measured again, after the treatment, the PL intensity was enhanced again, in order to find the reason, the temperature-dependent PL was measured, as the result showed that the GaN nanorod treated with KOH solution showed higher IQE than the untreated one.