AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuP

Paper EM-TuP22
Effect of Fluorine-Neutral Beam Irradiation on the Ohmic Contact Formation to n-type GaN

Tuesday, November 1, 2005, 4:00 pm, Room Exhibit Hall C&D

Session: Electronic Materials and Processing Poster Session
Presenter: H.C. Lee, Sungkyunkwan University, Korea
Authors: H.C. Lee, Sungkyunkwan University, Korea
J.W. Bae, Sungkyunkwan University, Korea
B.J. Park, Sungkyunkwan University, Korea
G.Y. Yeom, Sungkyunkwan University, Korea
Correspondent: Click to Email
Irradiation of a fuorine-neutral beam to n-type GaN surface is expected to create nitrogen vacancy at the near surface region of the GaN due to the removal of nitrogen by forming NFx(x=1-3) volatile gases, which may act as donor impurities. In the case of n-type GaN contact formation, it is well known that the increase in the donor concentration at the surface region of the GaN is one of important factors to achieve a good ohmic formation. The increase of carrier concentration should lead to a decrease of the effective barrier height between n-GaN and contact material, implicating a decrease of the depletion region width. Consequently, more carriers can tunnel through the reduced barrier, resulting in ohmic contact behavior. To date, few investigators have been using chlorine-based plasmas to generate N-vacancies at the surface region of the GaN. However, these charged and energetic treatments may lead to an electrical damage to the GaN layer, which can be attributed to the deterioration of contact property. On the other hand, a treatment by a neutral beam may give no electrical damage to the GaN layer due to its neutrality. It is noteworthy that the creation of N vacancy without electrical damage causes an increase in the net carrier concentration in the near surface region of n-GaN, resulting in the decrease of the contact resistivity. Therefore, in this study, a fluorine-neutral beam is proposed to remove nitrogen atoms off at the surface of n-type GaN without electrical damage. The subsequent ITO-based contact schemes including ITO, Ti/ITO, and Cr/ITO have been investigated using a current-voltage measurement system, photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). In this presentation, the advantage of fluorine-neutral beam treatment to modify n-GaN surface, as compared to a reactive ion treatment will also be discussed.