Low Resistance Ohmic Contact on Epitaxial MOVPE Grown β-Ga2O3 and β-(AlxGa1-x)2O3 Films

We report on the realization of record low resistance Ohmic contacts to MOVPE-grown heavily Si-doped beta-Ga2O3 and beta-(AlxGa1-x)(2)O-3 epitaxial films. Transfer length measurement (TLM) patterns were fabricated on the heavily Si-doped homoepitaxial beta-Ga2O3 films with electron concentration (n) ranging from 1.77 to 3.23x10(20) cm(-3) . Record low specific contact resistance (rho(c)) and total contact resistance (R-c) of 1.62x10(-7) Omega.cm(2) and 0.023 Omega.mm were realized for beta-Ga2O3: Si films with n > 3 x 10(20) cm(-3). TLM structures were also fabricated on heavily Si doped coherently strained beta-(AlxGa1-x)(2)O-3/beta-Ga2O3 (x=12%, 17% and 22%) films. The film with 12% Al composition (n = 1.23 x 10(20) cm(-3) ) showed rho(c) of 5.85x10(-6) Omega.cm(2) , but it increased to 2.19x10(-4) Omega.cm(2) for a layer with a 22% Al composition. Annealing the samples post metal deposition has generally led to a decrease in contact resistance, but for high Al content beta-(AlxGa1-x)(2)O-3, the contact resistance did not change significantly after the annealing process. The low contact resistance values measured in this work are very promising for the fabrication of high frequency power devices.

Automated summary

We report the realization of record low resistance Ohmic contacts to MOVPE-grown heavily Si-doped beta-Ga2O3 and beta-(AlxGa1-x)(2)O-3 epitaxial films. Transfer length measurement (TLM) patterns were fabricated on the heavily Si-doped homoepitaxial beta-Ga2O3 films, achieving record low specific contact resistance and total contact resistance for films with high electron concentration (n > 3 x 10^20 cm^−3). TLM structures were also fabricated on heavily Si doped coherently strained beta-(AlxGa1-x)(2)O-3/beta-Ga2O3 films, showing a change in contact resistance with varying Al composition.