Systematic characterization of Cl2 reactive ion etchingfor improved ohmics in AlGaN/GaN HEMTs
Buttari, D.; Chini, A.; Meneghesso, G.; Zanoni, E.; Moran, B.; Heikman, S.; Zhang, N.Q.; Shen, L.; Coffie, R.; DenBaars, S.P.; Mishra, U.K.
Electron Device Letters, IEEE
Volume 23, Issue 2, Feb 2002 Page(s):76 - 78
Digital Object Identifier 10.1109/55.981311
Summary:Pre-metal-deposition reactive ion etching (RIE) was performed on
an Al0.3Ga0.7N/AlN/GaN heterostructure in order to
improve the metal-to-semiconductor contact resistance. An optimum AlGaN
thickness for minimizing contact resistance was determined. An initial
decrease in contact resistance with etching time was explained in terms
of removal of an oxide surface layer and/or by an increase in tunnelling
current with the decrease of the AlGaN thickness. The presence of a
dissimilar surface layer was confirmed by an initial nonuniform etch
depth rate. An increase in contact resistance for deeper etches was
experienced. The increase was related to depletion of the
two-dimensional (2-D) electron gas (2-DEG) under the ohmics. Etch depths
were measured by atomic force microscopy (AFM). The contact resistance
decreased from about 0.45 Ωmm for unetched ohmics to a minimum of
0.27 Ωmm for 70 Å etched ohmics. The initial thickness of
the AlGaN layer was 250 Å. The decrease in contact resistance,
without excessive complications on device processing, supports RIE
etching as a viable solution to improve ohmic contact resistance in
AlGaN/GaN HEMTs
View citation and abstract |
Cart
