研究目的
The study aims to explore the interface properties of GaP/Si heterojunctions fabricated by a low temperature (less than 400 °C) III–V compounds on Si substrates using the plasma-enhanced atomic layer deposition (PE-ALD) technique, focusing on their influence on solar cell performance.
研究成果
The study concludes that the amorphous-GaP/Si interface fabricated with low RF power hydrogen plasma exhibits better photovoltaic performance compared to the epitaxial interface. The damage of Si near the interface, caused by high RF power hydrogen plasma, is identified as a key factor limiting the performance. A modified PE-ALD process without hydrogen plasma avoids this damage, suggesting a pathway for improving the quality of GaP/Si heterojunctions.
研究不足
The study identifies that high power hydrogen plasma treatment during the growth process can damage the near-surface area of Si substrates, leading to strong recombination losses. This damage is a significant limitation for the photovoltaic performance of the heterojunctions.
1：Experimental Design and Method Selection:
The study uses plasma-enhanced atomic layer deposition (PE-ALD) at 380 °C to grow GaP layers on p-type Si substrates. Different plasma treatments and RF power values are explored to study their effects on the interface properties.
2：Sample Selection and Data Sources:
p-type (0.8–1.2 ohm cm) B-doped CZ Si substrates of (001) orientation with 4° off cut toward [110] are used. Si wafers are cleaned by the Shiraki method followed by an HF-dip removal of oxide prior to the GaP deposition.
3：8–2 ohm cm) B-doped CZ Si substrates of (001) orientation with 4° off cut toward [110] are used. Si wafers are cleaned by the Shiraki method followed by an HF-dip removal of oxide prior to the GaP deposition.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Oxford PlasmaLab 100 PECVD setup for PE-ALD, phosphine (PH3) and trimethyl-gallium (TMG) as sources of phosphorus and gallium, JEOL JEM 2100F TEM for structural properties study, Keithley 2400 source-meter for I–V curves, Agilent 4980A LCR meter for admittance spectroscopy.
4：Experimental Procedures and Operational Workflow:
The PE-ALD process involves alternating phosphorus and gallium atom source flows. Different modes of deposition are used, including constant low RF power for amorphous GaP and pulsed RF power increase for microcrystalline GaP. Photoelectrical and electrical properties are measured under AM1.5G simulator.
5：5G simulator.
Data Analysis Methods:
5. Data Analysis Methods: Admittance spectroscopy (C-T-ω and G-T-ω) is used to detect interface states and defect levels. TEM studies are conducted to observe the structural properties of the GaP/Si interface.
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