AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThP

Paper EM-ThP10
Characteristics of Ohmic Contact Properties on N-polar Face n-type GaN with Dry and Wet Etching Method

Thursday, November 16, 2006, 5:30 pm, Room 3rd Floor Lobby

Session: Electronic Materials and Processing Poster Session
Presenter: T. Jang, Samsung Advanced Institute of Technology, Korea
Authors: T. Jang, Samsung Advanced Institute of Technology, Korea
Y.J. Sung, Samsung Advanced Institute of Technology, Korea
O.H. Nam, Samsung Advanced Institute of Technology, Korea
Y. Park, Samsung Advanced Institute of Technology, Korea
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Recently, remarkable progress on the development of blue and violet laser diode (BV-LD) has been made by several companies (Nichia, Sony and Samsung). BV-LD is a key component as a light source for high density optical storage systems and large scale display systems. Most of the commercialized high-power BV-LDs are fabricated on the free standing GaN wafers because of their high thermal conductivity, ease of cleaving and simple fabrication process. Free standing GaN wafer has a wurtzite crystal structure which has two different polarities along the c-axis direction, (0001) Ga face and (0001(_)) N face, respectively. The (0001) surface is composed of three nitrogen dangling bonds which points upward the c-plane surface, while (0001(_)) surface has a single nitrogen dangling bond that points upward. This difference in surface structure affects the device characteristics, especially ohmic contacts properties. Instead of using just Ga-face surface (0001), both Ga-polar face (0001) and N-polar face (0001(_)) surfaces would be used with free standing GaN wafers to fabricate LDs. One of the serious concerns in the fabrication of high-power BV-LDs is the difficulty of achieving reliable ohmic contact property on N-polar face n-type GaN. In this study, the effects of surface treatments such as ICP (Inductively Coupled Plasma) and wet etchings prior to the ohmic contact formation were investigated by measuring the contact resistivity of TLM (Transfer Length Method). Ohmic contact materials comprised of the layer sequence of Al/Ti and Pd/Ti/Al were deposited and contact resistivities were measured with respect to the annealing temperatures. The results of contact resistivity and AFM (Atomic Force Microscopy) confirmed that the area of contact is directly related to the improvement of ohmic contact property on N-polar face n-type GaN.