AVS 51st International Symposium
    Semiconductors Thursday Sessions
       Session SC+EM-ThM

Paper SC+EM-ThM5
Confined Epitaxial Growth of GaN for Defect Reduction and Device Development

Thursday, November 18, 2004, 9:40 am, Room 304B

Session: Wide Bandgap Semiconductors
Presenter: C.R. Eddy, Jr., Naval Research Laboratory
Authors: C.R. Eddy, Jr., Naval Research Laboratory
R.T. Holm, Naval Research Laboratory
R.L. Henry, Naval Research Laboratory
M.E. Twigg, Naval Research Laboratory
N.D. Bassim, Naval Research Laboratory
L.M. Shirey, Naval Research Laboratory
F.K. Perkins, Naval Research Laboratory
M.C. Peckerar, University of Maryland
E.J. Cukauskas, Sachs Freeman Associates
Correspondent: Click to Email
The family of III-V nitride materials has been the subject of many device technology development efforts, including visible and ultraviolet light emitters and detectors and high power rf transistors. Another area of interest is the development of vertically conducting device technologies for power electronics. In such applications it is critical that the threading dislocations inherent in this heteroeptixial materials system (no native substrate) be eliminated, particularly in the active region of the device. These threading dislocations have been identified as sources of leakage currents and premature failure of voltage blocking devices. In this work, an approach to reduce/eliminate vertical threading dislocations is described and initial results presented. The approach involves confined homo- or hetero-epitaxy of GaN materials using sputtered oxide masks to delineate growth regions. Growth is carried out using conventional MOCVD and conditions that inhibit lateral growth over the mask. The resulting confined epitaxial material is terminated with equilibrium crystal facets that form hexagonal mesas. The material contains a reduced dislocation density (approximately one order of magnitude as determined by TEM) compared to the underlying template layer for homoepitaxial growth. This reduction in dislocation density is believed to be the result of reduced strain in the epitaxial volume and the presence of the free surfaces represented by the sidewalls of the mesa. Characterization of pn junction diodes grown in this manner reveals significantly reduced leakage currents in as-grown structures (1 @mu@A/cm@super2@), which can be further reduced with application of passivation coatings. The approach is well suited to the development of distributed diode device technologies appropriate for power device applications. Issues such as doping variations in the confined epitaxial regions and the impact of additional device filtering techniques will also be presented.