A method has been developed for inserting submonolayer (SML) quantum dots (QDs) or SML QD stacks, instead of conventional Stranski-Krastanov (S-K) QDs, into the active region of intersubband photodetectors. A typical configuration would be InAs SML QDs embedded in thin layers of GaAs, surrounded by AlGaAs barriers. Here, the GaAs and the AlGaAs have nearly the same lattice constant, while InAs has a larger lattice constant.
In QD infrared photodetector, the important quantization directions are in the plane perpendicular to the normal incidence radiation. In-plane quantization is what enables the absorption of normal incidence radiation. The height of the S-K QD controls the positions of the quantized energy levels, but is not critically important to the desired normal incidence absorption properties. The SML QD or SML QD stack configurations give more control of the structure grown, retains normal incidence absorption properties, and decreases the strain build-up to allow thicker active layers for higher quantum efficiency.
This work was done by David Z. Ting, Sumith V. Bandara, and Sarath D. Gunapala of Caltech and Yia-Chung Chang of the University of Illinois for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Physical Sciences category. NPO-46115
This Brief includes a Technical Support Package (TSP).
Submonolayer Quantum Dot Infrared Photodetector
(reference NPO-46115) is currently available for download from the TSP library.
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Overview
The document presents a Technical Support Package for the Submonolayer Quantum Dot Infrared Photodetector (SML-QDIP), developed by NASA's Jet Propulsion Laboratory. This innovative technology aims to enhance infrared detection capabilities by utilizing embedded quantum dots (QDs) within a semiconductor matrix. Traditional quantum well infrared photodetectors (QWIPs) face limitations due to lattice mismatches between the quantum dot material and the host semiconductor, which can lead to strain build-up and degradation of the material when attempting to grow thick layers of QD-based active regions.
The SML-QDIP addresses these challenges by incorporating submonolayer quantum dots, which are formed by inserting typically 2 to 3 monolayers of a semiconductor, such as InAs, into a host matrix like GaAs. This approach reduces strain build-up, allowing for the growth of thicker active absorbing materials, which ultimately enhances the absorption and quantum efficiency of the detector. The SML-DWELL configuration retains the necessary nano-size in-plane dimensions for lateral quantization, crucial for normal incidence absorption properties, while using quantum well widths and barriers to control quantization in the normal-to-plane direction.
The document emphasizes the novelty of the SML-QDIP, highlighting its ability to maintain normal incidence absorption properties while providing greater control over the structure and reducing strain. This advancement is significant for applications in infrared detection, where improved performance is essential.
The Technical Support Package is part of NASA's Commercial Technology Program, aimed at disseminating aerospace-related developments with potential wider technological, scientific, or commercial applications. It includes contact information for further inquiries and emphasizes that the document is subject to export control regulations.
Overall, the SML-QDIP represents a promising advancement in infrared detection technology, leveraging the unique properties of submonolayer quantum dots to overcome the limitations of traditional quantum dot and quantum well structures, thereby paving the way for enhanced performance in various applications.
