研究目的
To perform depth profiling of the ambipolar carrier lifetime in thick n-type silicon carbide epilayers using two-photon absorption and time-resolved photoluminescence decay for non-destructive analysis.
研究成果
The carrier lifetime depth profile was successfully measured in thick n-type SiC epilayers using TPA excitation and TRPL decay, providing non-destructive analysis with 10 μm depth resolution. Lifetime variations indicate surface and interface recombination effects and distribution of carbon vacancies, useful for optimizing high-voltage device performance.
研究不足
The technique assumes a semi-infinite epilayer model, which may not fully account for finite thickness effects in very thin layers. Depth resolution is limited to approximately 10 μm, and the method requires specific laser equipment and expertise.
1：Experimental Design and Method Selection:
The study uses two-photon absorption (TPA) excitation with a pulsed 586 nm laser and confocal measurement of time-resolved photoluminescence (TRPL) decay to profile carrier lifetime depth in SiC epilayers. A semi-infinite model accounts for TPA excitation, carrier diffusion, and surface/interface recombination.
2：Sample Selection and Data Sources:
A commercially obtained n-type 4H-SiC epilayer, 140 μm thick, doped at 1x10^14 cm^-3, grown on a 4° offcut SiC substrate.
3：List of Experimental Equipment and Materials:
Mode-locked cavity-dumped dye laser (wavelength 586 nm, pulse width 1 psec, pulse energy 750 pJ, repetition rate 500 kHz), confocal microscope with 100x, 0.7 NA objective lens, Newport XYZ translation stage (10 nm precision), cooled photomultiplier (PMT) with 390±10 nm bandpass filter, fast Ortec photon counting card.
4：7 NA objective lens, Newport XYZ translation stage (10 nm precision), cooled photomultiplier (PMT) with 390±10 nm bandpass filter, fast Ortec photon counting card.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The laser beam is focused into the sample using the objective lens, with the translation stage varying the focal point depth. PL is collected via the PMT and analyzed for decay curves at different depths.
5：Data Analysis Methods:
Injected carrier density is calculated using equations for TPA. TRPL decay curves are fitted using a model that includes diffusion and recombination, with non-linear least squares optimization to extract lifetime profiles.
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