Applied Physics Letters, Vol. 112, 2018, DOI:

Electrical characterization of ALD HfO2 high-k dielectrics on ( 201) β-Ga2O3

D. I. Shahina, Aris Christoua, Marko J. Tadjerb, Virginia D. Wheelerb, Andrew D. Koehlerb, Travis J. Andersonb, Charles R. Eddy, Jr.b

a Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
b U.S. Naval Research Laboratory, Washington, District of Columbia 20375, USA


The electrical quality of HfO2 dielectrics grown by thermal atomic layer deposition at 175 C on n-type (201) β-Ga2O3 has been studied through capacitance- and current-voltage measurements on metal-oxide-semiconductor capacitors. These capacitors exhibited excellent electrical characteris- tics, including dual-sweep capacitance-voltage curves with low hysteresis and stretch-out and a frequency-stable dielectric constant of k14 when measured between 10 kHz and 1 MHz. The C-V curves exhibited a uniform and repeatable þ1.05 V shift relative to the ideal case when swept from 3.5 to 5 V, yielding positively measured flatband (þ2.15 V) and threshold (þ1.05 V) voltages that may be useful for normally off n-channel Ga2O3 devices. Using the Terman method, an average interface trap density of 1.3 1011 cm2 eV1 was obtained between 0.2 and 0.6 eV below the conduction band edge. The forward bias current-voltage characteristic was successfully fitted to the Fowler-Nordheim tunneling model at a field strength of 5 MV/cm, allowing an extraction of a 1.3 eV conduction band offset between HfO2 and Ga2O3, which matches the value previously deter- mined from x-ray photoelectron spectroscopy. However, a temperature dependence in the leakage current was observed. These results suggest that HfO2 is an appealing dielectric for Ga2O3 device applications.

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