Low-resistance ohmic contacts on p-type GaN using Ni/Pd/Au metallization

Abstract

Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices J. Appl. Phys. 112, 063714 (2012) Polarization Coulomb field scattering in In0.18Al0.82N/AlN/GaN heterostructure field-effect transistors J. Appl. Phys. 112, 054513 (2012) Modulation doping to control the high-density electron gas at a polar/non-polar oxide interface Appl. Phys. Lett. 101, 111604 (2012) Ultra low-resistance palladium silicide Ohmic contacts to lightly doped n-InGaAs

Photosensitivity Analysis of Gallium Nitride and Silicon Carbide Terahertz IMPATT Oscillators: Comparison of Theoretical Reliability and Study on Experimental Feasibility

“…On the other hand, for p-type GaN, because of the difficulty in achieving high carrier density and the absence of suitable metals with high work function, a high-quality ohmic contact with very low contact resistivity (∼10 −7 Ω · cm 2 ) is still not achieved. For p-type GaN, however, the best result (4.5 × 10 −6 Ω · cm 2 ) could be obtained from the Be-doped (Concentration 8.1 × 10 19 cm −3 ) sample with Ni/Pd/Au contacts [22]. A very recent study showed that ohmic contacts to n-SiC are formed by using a pure Ni-based layer with a thin underlying Si layer.…”

“…A specific contact resistance of 1.0 × 10 −4 Ω · cm 2 can be achieved in this technique. If a similar metal composition is deposited on the Be-implanted p ++ -type GaN layer with a carrier density of 8.1 × 10 19 cm −3 , without further annealing process, the sample will show good ohmic contact with a contact resistance of 4.5 × 10 −6 Ω · cm 2 [22]. A new metallization scheme has recently been developed for obtaining very low ohmic contact to n-GaN [21].…”

“…Using photolithography and liftoff techniques, low-resistance contact metals, an alloy of Ni (20 nm)/Pd (20 nm)/Au (100 nm) [22], can be deposited inside the windows by an electron beam evaporator. The metal contacts should then be annealed in air, nitrogen, and oxygen ambient conditions at different annealing temperatures ranging from 350 • C to 650 • C. The measurement of specific contact resistance may be done by a circular TLM (CTLM) system.…”

Wide-Bandgap III–V nitride based avalanche transit-time diode in Terahertz regime: Studies on the effects of punch through on high frequency characteristics and series resistance of the device

“…For p-type GaN, however, the best result (4.5 Â 10 À6 X cm 2 ) could be obtained from Be-doped (conc. 8.1 Â 10 19 cm À3 ) sample with Ni/Pd/Au contacts [19]. It is not worthy to mention that, in order to get appreciable power (Watt level) from a THz source, low specific contact resistance ($10 À7 X cm 2 ) should be achieved, since at THz region intrinsic diode negative resistance is usually very small.…”

Nanopatterned Contacts to GaN

“…A large variety of elemental and multicomponent metallizations have been explored for ohmic contacts to n-GaN and p-GaN. [3][4][5][6][7][8] Additionally, various surface treatment techniques such as wet chemical surface modification, 9 dry etching, 10 and laser etching 11 have been used to reduce the ohmic contact resistance, yet specific contact resistances are still sufficiently high so as to impact device performance, particularly for p-GaN.…”