Optical studies of  Reactive Ion Etched GaN

A. General

We are developing technology to produce nano-scale semiconductor structures using Reactive Ion Etching (RIE). The combination of optical characterisation tools at visible and infra-red wavelengths, together with Raman spectroscopy are providing valuable information on the etching process, leading to optimisation of the technique.

B. Specific project: damage induced in GaN by RIE

RIE is a key aspect in integrated circuit engineering and serves to transfer a pre-defined pattern into the required substrate anisotropically through an interplay between chemical reactive radicals and physical ion bombardment in a plasma. It has proven its capability for well-controlled and accurate pattern transfer, having high spatial resolution, for a variety of applications utilising a diversity of materials. However, as reactive ion etching becomes more widely and routinely applied for the fabrication of nanometre-scale devices, it becomes important to understand the possible damage to the material, introduced by the processing itself. Full understanding of the complexity of interactions that propagate damage into the etched material, which accounts for variations in material composition, etch gas chemistry, etch technique, is as multifaceted problem as understanding the detailed reactions and components of the etch process itself. We want to understand etch-induced changes, effects that determine the limits of resolution in the reactive ion etching. The chemical stability of GaN provides the ultimate technological challenge for pattern transfer into the substrate. So far, no reliable wet etchant has been found for GaN.

This work brings together researchers in the Department of Physics and Astronomy, the Department of Electrical and Electronic Engineering, and the Department of Optoelectronics at the University of Ulm in Germany.

C. Recent Success

Our recent work has been highly productive. Some of the results can be seen in: 

S. A. Brown, R. J. Reeves, C. S. Haase, R. Cheung, C. Kirchner and M. Kamp 'Reactive Ion Etched Gallium Nitride: Metastable Defects And Yellow 
Luminescence'. Applied Physics Letters 75, 3285 (1999). 

R. Cheung, S. Withanage, R. J. Reeves, S. A. Brown, I. Ben-Yaacov, C. Kirchner and M. Kamp, 'Reactive ion etch-induced effects on the near-band-edge 
luminescence in GaN', Applied Physics Letters 74, 3185 (1999). 

D. Student Projects

Over the last three years there have been a significant number of successful honours projects in this area, and Bifeng Rong has made a great deal of progress toward a Ph.D. A number of other Ph. D. Projects are available in this area.

E. Amorphous GaN

We have recently begun a NERF funded project to produce amorphous GaN in collaboration with Prof Joe Trodahl at Victoria Uni