Wavelength independent normal incident quantum cascade detectors

Area of Science:

• Optoelectronics
• Infrared Spectroscopy
• Semiconductor Devices

Background:

• Intersubband infrared detectors typically require angled light incidence for optimal absorption.
• Achieving efficient normal-incident absorption is crucial for practical sensor applications.
• Current methods often involve complex fabrication or limited wavelength ranges.

Purpose of the Study:

• To demonstrate a novel technique for normal-incident absorption in intersubband infrared detectors.
• To investigate the performance of specifically designed quantum cascade detectors (QCDs) utilizing this technique.
• To compare the performance of novel detector designs with standard detectors.

Main Methods:

• Fabrication of spiral and hairpin shaped quantum cascade detectors using wet-etching.
• Utilizing light scattering from mesa side-walls to enhance normal-incident absorption.
• Comparison of responsivity and detectivity of novel designs against a standard rectangular mesa detector.

Main Results:

• Spiral and hairpin detectors achieved peak responsivities of 6 mA/W and 12 mA/W, respectively, at normal incidence.
• Detectivity for spiral and hairpin detectors reached approximately 3x10^10 cmHz/W at 80 K, a significant improvement over standard detectors.
• The novel method demonstrated wavelength independence and comparable performance to 45-degree incidence in standard detectors.

Conclusions:

• Light scattering from mesa side-walls is an effective technique for achieving normal-incident absorption in intersubband detectors.
• The spiral and hairpin designs show significant performance enhancements, particularly in detectivity.
• This fabrication-friendly method facilitates the widespread adoption of intersubband detectors in various sensor applications.