Design and performance of GaSb-based quantum cascade detectors

Area of Science:

• Semiconductor Physics
• Optoelectronics
• Materials Science

Background:

• InAs/AlSb heterostructures offer unique electronic and optical properties for advanced detector applications.
• Strain-balanced growth on GaSb substrates is crucial for achieving high-quality InAs/AlSb heterostructures.
• Quantum Cascade Detectors (QCDs) leverage intersubband transitions for tailored infrared detection.

Purpose of the Study:

• To design and fabricate novel InAs/AlSb quantum cascade detectors (QCDs) on GaSb substrates with enhanced performance.
• To explore strain engineering using submonolayer InSb layers to optimize detector design and material properties.
• To investigate the optical and electrical characteristics of these QCDs across a range of wavelengths.

Main Methods:

• Utilized strain-balanced epitaxy of InAs/AlSb on GaSb substrates with controlled InAs:AlSb ratios.
• Introduced submonolayer InSb layers to engineer strain and achieve lattice-matched conditions for detector design.
• Designed and grew four active regions with varying InAs:AlSb ratios for mid-infrared detection (3.65–5.5 µm).
• Characterized the fabricated QCDs for responsivity, detectivity, and spectral response at room temperature.

Main Results:

• Achieved a room-temperature peak responsivity of 26.12 mA/W and a detectivity of 1.41 × 10^8 Jones for an optimized QCD at 4.3 µm.
• Demonstrated successful strain engineering enabling high InAs:AlSb thickness ratios (up to 2.8:1) for tailored active region designs.
• Observed higher-energy interband signals in the mid- to near-infrared due to type-II alignment and narrow InAs band gap.

Conclusions:

• Strain-balanced InAs/AlSb QCDs on GaSb substrates are a promising platform for high-performance infrared detection.
• Strain engineering with submonolayer InSb is an effective strategy to optimize QCD design and overcome lattice-matching limitations.
• The developed QCDs exhibit excellent room-temperature performance and potential for broadband infrared sensing applications.