研究目的
To investigate the barrier height modification in Au/Ti/n-GaAs devices with a HfO2 interfacial layer formed by atomic layer deposition, and to characterize the electrical properties and surface morphology of these structures.
研究成果
The HfO2 interfacial layer effectively increases the barrier height in Au/Ti/n-GaAs devices, with values of 1.03 eV and 0.93 eV for 3 nm and 5 nm layers, respectively, at 300 K, compared to 0.77 eV without HfO2. The bias-dependent barrier heights from Gaussian distribution and Norde's method are in agreement, confirming the utility of HfO2 for barrier modification in GaAs-based devices like MOS capacitors and MOSFETs.
研究不足
The study is limited to specific HfO2 thicknesses (3 nm and 5 nm) and may not generalize to other thicknesses or materials. The presence of interface states and inhomogeneities could affect device performance, and the ALD process requires precise control to avoid defects.
1：Experimental Design and Method Selection:
The study involves fabricating Au/Ti/HfO2/n-GaAs MIS structures using atomic layer deposition for HfO2 growth, with electrical characterization via I-V and C-V measurements over a temperature range of 60-400 K. Theoretical models include thermionic emission theory, Norde's method, and Gaussian distribution of barrier heights.
2：Sample Selection and Data Sources:
n-type GaAs wafers with (100) orientation, thickness of 300 μm, diameter of 2 inch, resistivity of 1.2 Ωcm, and carrier concentration of 6.8 × 10^15 cm^-3 were used. Data were collected from fabricated devices.
3：2 Ωcm, and carrier concentration of 8 × 10^15 cm^-3 were used. Data were collected from fabricated devices.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a Savannah S100 ALD reactor for HfO2 deposition, magnetron DC sputter for Ti contacts, high-vacuum evaporation system for Au, HP 4192A LF impedance analyzer for C-V measurements, Leybold Heraeus closed-cycle helium cryostat and Keithley 487 Picoammeter Voltage Source for I-V measurements, XPS (SPECS) for surface characterization, and AFM for morphology analysis. Materials include Hf(NMe2)4 precursor, H2O, N2 carrier gas, HF solution, Ti, Au, and GaAs substrates.
4：Experimental Procedures and Operational Workflow:
Native oxide removal with HF, HfO2 deposition via ALD at 200°C with specific pulse and purge times, fabrication of Schottky contacts by sputtering Ti and evaporating Au, followed by electrical measurements in dark conditions across temperature ranges.
5：Data Analysis Methods:
Data were analyzed using thermionic emission equations, Norde's method for series resistance and bias-dependent barrier height, Gaussian distribution models for barrier inhomogeneity, and modified Richardson plots.
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