研究目的
Investigating the electrical properties of the AlN/4H-SiC interface, including interface trap density, electron trapping behavior, and breakdown characteristics, to explore AlN as a potential gate dielectric for SiC MIS devices.
研究成果
The AlN/4H-SiC interface shows an order of magnitude lower interface trap density at room temperature compared to nitrided SiO2/SiC interfaces, but significant electron trapping occurs in bulk AlN traps under accumulation bias, which is reversible with depletion bias at elevated temperatures. Breakdown field is 3-4 MV/cm, improved by adding a SiO2 layer. Future work should focus on thinner AlN layers with SiO2 capping to reduce trapping and enhance device applicability.
研究不足
The AlN layers exhibit significant electron trapping under accumulation bias, leading to large flatband voltage shifts and limited breakdown field (3-4 MV/cm). The origin of bulk traps is unknown, potentially due to defects or dislocations. High-density shallow interface traps near the SiC conduction band edge are detected at low temperatures, which may affect device performance. The study is limited to capacitor structures; implications for MOSFET channel mobility are not fully established.
1：Experimental Design and Method Selection:
The study involves fabricating MIS capacitors with AlN gate dielectric grown by MOCVD and analyzing them using CV and IV measurements to assess interface and bulk trap densities, electron trapping, and breakdown properties. Theoretical models include Fowler-Nordheim tunneling for barrier height estimation.
2：Sample Selection and Data Sources:
Samples include n-type 4H-SiC epitaxial layers with various dielectric configurations (single AlN layers and stacks with SiO2, Al2O3, or Si3N4). Reference samples with thermally grown SiO2 are used for comparison.
3：4). Reference samples with thermally grown SiO2 are used for comparison. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a hot-wall MOCVD reactor for AlN growth, PECVD, ALD, and LPCVD systems for additional dielectric layers, Agilent E4980A LCR meter for CV measurements, Keithley 617 electrometer for IV measurements, AFM for morphology characterization, and a vacuum cryostat for measurements.
4：Experimental Procedures and Operational Workflow:
Steps include SiC surface cleaning, AlN growth at 1100°C, deposition of additional dielectric layers, metallization with aluminum, patterning by lithography, and electrical measurements at various temperatures and biases.
5：Data Analysis Methods:
Data analysis involves extracting interface trap density from CV dispersion, calculating trapped electron density using flatband voltage shifts, and determining breakdown field and barrier height from IV curves using Fowler-Nordheim tunneling theory.
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LCR meter
E4980A
Agilent
Performing capacitance-voltage (CV) and conductance-voltage (GV) measurements on MIS capacitors.
E4980A/E4980AL Precision LCR Meter
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Electrometer
617
Keithley
Performing current-voltage (IV) measurements to determine dielectric breakdown strength and tunneling barrier height.
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Atomic Force Microscope
Characterizing the morphology of AlN/SiC samples.
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MOCVD reactor
hot-wall
Growing crystalline AlN layers on SiC substrates.
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PECVD system
Depositing SiO2 layers.
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ALD system
Growing Al2O3 layers.
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LPCVD system
Depositing Si3N4 layers.
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Cryostat
Cooling samples for measurements at low temperatures (e.g., 77 K).
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