AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThP

Paper EM-ThP12
Etch Characteristics of GaN using Chemically Assisted Ion Beam Etching(CAIBE) and Its Effects on Ohmic Contact Formation to n-type GaN

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Electronic Materials and Processing Poster Session
Presenter: W.J. Lee, Sungkyunkwan University, Korea
Authors: W.J. Lee, Sungkyunkwan University, Korea
G.Y. Yeom, Sungkyunkwan University, Korea
J.W. Lee, Samsung Advanced Institute of Technology, Korea
Y.J. Park, Samsung Advanced Institute of Technology, Korea
T.I. Kim, Samsung Advanced Institute of Technology, Korea
Correspondent: Click to Email
Currently, GaN facets required for GaN laser devices are fabricated using dry etching due to the difference in the cleavage planes of sapphire substrates and GaN epitaxial layers grown on them. Fabrication of GaN facets using dry etching not only requires high GaN etch rates, high selectivity over mask layers, and vertical etch profile with a smooth sidewall, but also requires damage-free etch surface which could be induced due to the energetic ion bombardment during the etching. This induced damage could degrade the electrical performance of the device. Therefore, in this study, we investigated the etch properties, etch-induced damage, and resistances of contacts formed on etched n-type GaN. The GaN samples used in the experiment were grown by metalorganic chemical vapor deposition on sapphire substrates and GaN etching was performed using CAIBE system(RF-350 Etching System, Veeco) having a 210mm diameter ion source, a Meissner trap, and a load-lock chamber. Ar was introduced into the ion source while Cl@sub2@, BCl@sub3@, and HCl were distributed around the substrate through the nozzle. GaN samples patterned with PR or SiO@sub2@ were loaded on the rotational fixture which could be tilted between 0° and 60° and also could be heated up to 300 C or cooled down to 0 C. To determine the etch characteristics, GaN samples were etched as a function of Ar ion beam parameter, gas chemistry, tilt angle, and substrate temperature. Etch characteristics such as etch rates, selectivities, and etch profiles were estimated using a profilometer and scanning electron microscopy(SEM). Variation of surface composition of the etched GaN samples was investigated using X-ray photoelectron spectroscopy(XPS). Contact resistances of the etched n-type GaN samples were measured by transmission line measured(TLM) and physical damage on the etched GaN surface was observed using HRTEM. The relations of surface composition and physical damage on GaN surface to the ohmic contact resistances were also studied.