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Digital Alloy-Grown InAs/GaAs Short-Period Superlattices with Tunable Band Gaps for Short-Wavelength Infrared
Bingtian Guo1, Baolai Liang2, Jiyuan Zheng3
1Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia 22904, United States.
ACS Photonics
|April 22, 2024
Summary
Digital alloy (DA) grown InAs/GaAs superlattices extend infrared photodetection. These superlattices show tunable band gaps and enhanced absorption, offering a promising alternative to random alloy InGaAs for advanced photodetectors.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Optoelectronics
Background:
- Indium Gallium Arsenide (InGaAs) is crucial for short-wavelength infrared photodetection.
- Extending the absorption spectral range of InGaAs is vital for advanced imaging and optical communications.
Purpose of the Study:
- To investigate digital alloy (DA)-grown InAs/GaAs short-period superlattices for extended infrared absorption.
- To explore band gap tunability and optical properties of DA InGaAs.
Main Methods:
- Scanning transmission electron microscopy (STEM)
- High-resolution X-ray diffraction (HRXRD)
- Atomic force microscopy (AFM)
- Photoluminescence (PL) spectroscopy
- Ellipsometry
- Environment-dependent tight binding (EDTB) model simulations
Main Results:
- DA-grown superlattices exhibit good material quality and tunable band gaps.
- Photoluminescence peaks shifted from 1690 nm (RA InGaAs) to 1950 nm (8 ML DA InGaAs).
- Absorption coefficients at 2 μm increased with ML thickness, reaching 1230 cm⁻¹ for 10 ML DA InGaAs.
- Red shift in absorption edge observed with increasing period thickness.
- Simulated band structures align with experimental PL data.
Conclusions:
- DA-grown InAs/GaAs superlattices offer significant band gap tunability and extended absorption.
- These materials are promising for photodetectors beyond the limits of conventional InGaAs.
- Band structure engineering via DA growth provides a pathway for tailored optoelectronic properties.
