Self‐assembled GaN nanostructures by dry etching and their optical properties

Abstract

The influence of process parameters and template characteristics on the morphology and optical properties of self-assembled nanostructures produced by dry etching from GaN/sapphire templates was investigated. It was found that the chemical component in the etching gas-chlorine supports the formation of nanostructures and that a minimum amount of RF and ICP power (i.e., energy) is necessary. Additionally the crystalline imperfec-tion and the doping concentration of the template greatly affect the nanostructure morphology. All nanostructures exhibit higher luminescence intensity than the templates they are fabricated from and exhibit a red-shift of the luminescence with respect to the epilayer. The results indicate effective strain relaxation as well as more efficient absorption of the incoming photons the smaller the nanostructures become.

The Role of Si during the Growth of GaN Micro- and Nanorods

“…Basically the inner part of the rods is etched. Some needle-like nanostructures remain, which are already known from RIE experiments of GaN layers . It was shown in ref that most of the rods contain vertical defects, which are separating regions of different polarity.…”

“…It was shown in ref that most of the rods contain vertical defects, which are separating regions of different polarity. It is assumed that preferential etching occurs along these defects . However, during RIE the sidewall facets are constantly exposed to the etching process, and at least some damage is expected.…”

“…A similar mechanism is expected as for the nanostructures formed during the RIE experiments (cf. Figure and ref ), that is, etching of crystalline imperfections. Both doped and undoped rods are of same N-polarity (except the small inversion domain in the center of the rod with Ga-polarity, cf.…”

“…Both effects might lead to different etching behavior. The defective material is assumed to be etched faster yielding the residual conical shaped nanostructures . The thermal stability of the nanorods is certifying suitability for high power devices and operation under harsh conditions, for example, concentrated photovoltaics and space applications.…”

“…Transmission electron microscopy (TEM) and EDX measurements were carried out at an acceleration of 200 kV in an FEI Titan 3 80–300 microscope equipped with an imageside aberration corrector. All details concerning MOVPE growth, SEM, CL, RIE, and TEM can be found in refs , , , and .…”