Potter, Richard, Partida, Teresa and Roberts, Joseph (2015) Comparative analysis of the effects of tantalum doping and annealing on atomic layer deposited (Ta2O5)x(Al2O3)1x dielectrics for GaN/AlxGa1xN/GaN high electron mobility.transistors applications . [Data Collection]
Description
This paper describes a method to optimally combine wide band gap Al2O3 with high dielectric constant (highκ) Ta2O5 for gate dielectric applications. (Ta2O5)x(Al2O3)1x thin films deposited by thermal atomic layer deposition (ALD) on GaNcapped AlxGa1xN/GaN high electron mobility transistor (HEMT) structures have been studied as a function of the Ta modulation doping. Xray photoelectron spectroscopy shows that the bandgap of the oxide films linearly decreases from 6.5 eV for pure Al2O3 to 4.6 eV for pure Ta2O5. The dielectric constant calculated from capacitancevoltage measurements also increases linearly from 7.8 for Al2O3 up to 25.6 for Ta2O5. The effect of postdeposition annealing in N2 at 600 ºC on the interfacial properties of undoped Al2O3 and Tadoped (Ta2O5)0.12(Al2O3)0.88 films grown on GaNHEMTs has been investigated. These conditions are analogous to the conditions used for source/drain contact formation in gatefirst HEMT technology. A reduction of the GaO to GaN bond ratios at the oxide/HEMT interfaces is observed after annealing, which is attributed to a reduction of interstitial oxygenrelated defects. As a result, the conduction band offsets (CBOs) of the Al2O3/GaNHEMT and (Ta2O5)0.16(Al2O3)0.84/GaNHEMT samples increased by 1.1 eV to 2.8 eV and 2.6 eV respectively, which is advantageous for ntype HEMTs. The results demonstrate that ALD of Tadoped Al2O3 can be used to control the properties of the gate dielectric, allowing the κvalue to be increased, while still maintaining a sufficient CBO to the GaNHEMT structure for low leakage currents.
Keywords: | Ta-doped Al2O3, GaN, HEMT |
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Divisions: | Faculty of Science and Engineering > School of Engineering |
Depositing User: | Richard Potter |
Date Deposited: | 10 Dec 2015 10:58 |
Last Modified: | 14 Dec 2015 15:33 |
DOI: | 10.17638/datacat.liverpool.ac.uk/77 |
URI: | https://datacat.liverpool.ac.uk/id/eprint/77 |
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