研究目的
Investigating the impact of net charge at the oxide/semiconductor interface (Qint) on threshold voltage instabilities in AlGaN/GaN metal-oxide-semiconductor heterostructures.
研究成果
The research demonstrates that high density of negative Qint in AlGaN/GaN MOS heterostructures leads to increased CV hysteresis and threshold voltage instabilities due to deep unoccupied interface states, making normally-off devices more susceptible. This highlights the importance of controlling Qint and interface quality for device stability, and suggests that CV hysteresis alone may not indicate high interface quality without considering Qint effects.
研究不足
The study assumes negligible configuration changes during charge capture/emission and does not fully account for bulk oxide trap contributions in some cases, as indicated by discrepancies in simulations for samples without PDA. The impact of different deposition methods and post-treatments on trap densities may vary.
1：Experimental Design and Method Selection:
The study used capacitance-voltage (CV) hysteresis measurements and 1-dimensional Poisson solver simulations with Shockley-Read-Hall model to account for interface trap capture/emission processes.
2：Sample Selection and Data Sources:
MOS heterostructures were processed on GaN-cap/AlGaN/GaN epitaxial heterostructures grown by metal-organic chemical vapor deposition (MOCVD) on sapphire substrates. Samples with and without post-deposition annealing (PDA) were compared.
3：List of Experimental Equipment and Materials:
Equipment includes X-ray reflectometry for oxide thickness measurement, CV measurement setup with 100 kHz frequency and 30 mV AC amplitude, Vth-transient measurement setup, filtered light-assisted Vth transient technique using a broadband Xe-lamp and band-pass filters, and materials such as Al2O3 gate oxide, Ti/Al/Ni/Au Ohmic contacts, and Ni/Au gate metal.
4：Experimental Procedures and Operational Workflow:
Steps included MESA isolation etching, Ohmic contact evaporation and annealing, Al2O3 deposition by MOCVD at 600°C with HCl dip and O2-plasma pretreatment, PDA at 700°C for some samples, CV hysteresis measurement with voltage sweeps from -12 V to positive voltages, and various techniques for Dit distribution measurement.
5：Data Analysis Methods:
Data were analyzed using Poisson solver simulations, linear fits for Vth-tox dependence to extract Qint, and combination of methods (Vth-transient, light-assisted, and CV frequency dispersion) to determine Dit distributions.
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