Indigenous Development of 320 x 256 Focal-Plane Array Using InAs/InGaAs/GaAs Quantum Dots-In-A-Well Infrared Detectors for Thermal Imaging

Abstract

We report here the indigenous development of a 320  256 infrared focal-plane imager fabricated using an InAs quantum dots-in-a-well heterostructure, whose photoluminescence peak is at 1162 nm and activation energy is 187 meV. We discuss the fabrication and characterization of single-pixel detectors that can measure intersubband spectral responses with peak intensity at 9.3 m. Using the fabricated device, infrared images were captured at 50-90 K. Device optimization led to approximately 95% of the pixels in the imaging array being operational and a reasonably low noise equivalent temperature of approximately 100 mK at 50-60 K.Keywords: Focal-plane arrays, infrared detectors, photoluminescence peak, quantum dots, thermal imaging.NANOTECHNOLOGY -which deals with the growth and manipulation of materials at the atomic and molecular levels and facilitates the development of materials with specifically designed performance characteristics -is a key state-of-the-art technology being researched and developed worldwide. The Government of India aims to be technologically self-sufficient by developing advanced technologies indigenously. To this end, the Government has established silicon nanotechnology laboratories at prominent academic institutes such as the Indian Institutes of Technology (IITs) and the Indian Institute of Science, Bengaluru. Nanotechnological advances pertaining to III-V compounds facilitate the development of advanced high-performance devices such as infrared focal-plane arrays (IR FPAs), solar cells, lasers and highspeed devices. Quantum dot (QD) or dot-in-a-well (DWELL) IR FPAs are state-of-the-art devices that may help realize miniature sensor systems. III-V compounds have advantages such as high operating temperatures and low dark currents, resulting in their high performance and applicability. Therefore, the Indian Institute of Technology Bombay (IITB), in collaboration with the Indian Space Research Organisation (ISRO), is researching the design and development of III-V compound QD infrared photodetector/DWELL structure-based detectors, with a focus on GaAs-based QD/DWELL IR FPAs. In this communication, we discuss DWELL heterostructures and the development of a 320  256 FPA IR imager that has reasonably low noise equivalent differential temperature (NEDT).The electron-hole pairs or excitons are squeezed in a semiconductor crystallite whose radius is smaller than two times its exciton Bohr radius which is of the order of a few nanometres, leading to quantum confinement. QDs have confinement in all three directions whereas quantum wells and quantum wires have confinement in one and two directions respectively. The quantum energy levels can be predicted using the particle-in-a-box model in which the energies of states depend on the length of the box. The characteristics and properties of such materials differ from those of bulk materials. For example, the desired quantum levels of materials can be engineered and realized through appropriate material selection, growth and geometric arrangement. QD ...

Impact of linear alloy on strain coupled bilayer InAs/GaAs1-ySby quantum dot heterostructures

“…The performance of quantum dots (QDs) based photodetectors was superior to the other materials community because of their unique properties such as low dark current density, longer carrier relaxation time, controlled electron-phonon scattering, and high operating temperature [2,3]. Due to these aforementioned reasons, InAs QDs-based devices have been used in multiple optoelectronic applications such as medical imaging, night vision camera, lasers, and telecommunications [4,5]. For the last few decades, researchers have been continuously working on improving the performance of QD-based devices.…”