研究目的
To clarify the dominant paths of dark current and reduce it in a long-wave cascade-transport IR up-converter (CIUP) for improving detector performance in very-large-scale IR detection/imaging.
研究成果
The step-bound-to-miniband design is the most effective in reducing dark current in long-wave CIUPs, achieving higher signal-to-noise ratio and detectivity. This is due to reduced tunneling, thermionic emission, and thermally-assisted tunneling via superlattice barriers and deeper absorption QWs. Future work should develop high-detectivity long-wave IR CIUPs based on this design.
研究不足
The study focuses on unipolar structures without the emission region, potentially limiting full device performance analysis. Deviations in epitaxial parameters from design may affect results. Temperature and bias ranges used might not cover all operational conditions.
1：Experimental Design and Method Selection:
The study involves designing three band structures (miniband-to-miniband, bound-to-miniband, step-bound-to-miniband) for long-wave CIUPs to analyze dark current paths. Theoretical calculations using the Schr?dinger equation and self-consistent electron concentration distributions are performed. Experimental samples are fabricated and measured to validate the designs.
2：Sample Selection and Data Sources:
Samples A, B1, B2, and C are grown based on the three designs, with variations in absorption QW periods. Data include photocurrent spectra and dark current measurements at different temperatures and biases.
3：List of Experimental Equipment and Materials:
Metal-organic chemical vapor deposition (MOCVD) for wafer growth, semi-insulating GaAs substrates, Ni-Ge-Au alloy for electrodes, etching tools for mesa formation, and measurement setups for photocurrent and dark current.
4：Experimental Procedures and Operational Workflow:
Wafers are grown by MOCVD, etched into mesas, electrodes are sputtered and annealed. Photocurrent spectra are measured at 78 K, dark currents are measured versus bias voltage at different temperatures. Data analysis includes Arrhenius plots for activation energy calculation.
5：Data Analysis Methods:
Electron concentration distributions are calculated self-consistently. Dark current components are analyzed using WKB approximation for tunneling and Arrhenius model for thermionic emission. Activation energies are derived from slopes of Arrhenius plots.
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