Emerging Type‐II Superlattices of InAs/InAsSb and InAs/GaSb for Mid‐Wavelength Infrared Photodetectors

Abstract

Mid‐wavelength infrared (MWIR) photodetectors (PDs) are highly essential for environmental sensing of hazardous gases, security, defense, and medical applications. Mercury cadmium telluride (MCT) materials have been the most used detector in the MWIR range. However, it is plagued by several challenges including toxicity concerns, a high rate of Auger nonradiative recombination, a large band‐to‐band (BTB) tunneling current, nonuniformity, and the need for cryogenic cooling. Theoretically, it is predicted that type‐II superlattice (T2SL) materials can emerge as an alternative with the potential to outperform the current state‐of‐the‐art MCT PDs due to suppression of Auger recombination associated with bandgap engineering and reduced BTB tunneling current caused by the larger effective mass. Based on this theoretical prediction, it is believed that T2SL have the potential to operate at high temperatures and overcome the size, weight, and power consumption limitations of MCT. Herein, a detailed review of the fundamental material properties of T2SL PDs is provided while providing a comparison of the optical and electrical performances of Ga‐free (InAs/InAsSb) and Ga‐based (InAs/GaSb) T2SL PDs. Finally, recent advances in IR detection technologies including focal plane arrays and quantum cascade infrared photodetectors are explored.

Hot Electron Dynamics in InAs–AlAsSb Core–Shell Nanowires

“…This suggests that by the large excitation energy carriers are excited within the AlAsSb shell, and hence, associated shell states can be probed. Note that the probe energy of 0.62 eV is above the InAs bandgap, therefore ground-state bleaching is observed, but below the bandgap of the AlAsSb shell and also below the bandgap of the GaSb cap . Most semiconductors show positive TA after photoexcitation of charge carriers for probe energies below the bandgap because of intraband (excited state) absorption …”

“…This discrepancy may be either explained by a barrier at the InAs–AlAsSb interface or by fast (τ < 20 ps) diffusion from electrons toward the GaSb cap that is deposited on top of the shell (see band alignment depicted in Figure b). The conduction band minimum (CBM) of the GaSb cap is well below the CBM of the AlAsSb shell, which means that diffusion of electrons from the shell toward the cap is an irreversible process by the fast cooling of hot electrons. Given the thin layers and the strong fields, we expect that this process could be finished within a few ps .…”

“…Note that the probe energy of 0.62 eV is above the InAs bandgap, therefore ground-state bleaching is observed, but below the bandgap of the AlAsSb shell and also below the bandgap of the GaSb cap. 43 Most semiconductors show positive TA after photoexcitation of charge carriers for probe energies below the bandgap because of intraband (excited state) absorption. 44 By the importance of trap states in InAs and corresponding core− shell NWs, it seems natural to assign the long-lived TA signal to traps or alloy fluctuations within the shell.…”

Room Temperature Bias-Selectable, Dual-Band Infrared Detectors Based on Lead Sulfide Colloidal Quantum Dots and Black Phosphorus

“…However, such materials suffer from high fabrication cost and complexity, the need to consider lattice matching, surface passivation, and high noise at room temperature . Therefore, continuous effort has been made in seeking device architectures and materials which overcome some of these limitations, such as quantum-well IR photodetectors, , type-II superlattice photodetectors, , and more recently, the use of low-dimensional materials in quantum dot IR photodetectors − and two-dimensional material IR photodetectors …”

Carrier recombination dynamics and temperature dependent optical properties of InAs–GaSb heterostructures

“…Semiconductor heterostructures based on indium arsenide (InAs) and gallium antimonide (GaSb) have been a technological foundation for several decades. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Extensive research efforts have been devoted to utilizing the InAs/GaSb heterostructures to form a tunable bandgap for mid-to-long wavelength infrared photodetector applications. [1][2][3][4][5] The original InAs/GaSb type-II broken-gap band alignment [6][7][8][9] can be modified by the thickness of each layer to form a superlattice (SL) band structure, resulting in either a semimetallic (E G r 0) or a semiconducting (energy gap, E G 4 0) material system for a long or short period InAs/GaSb SLs, respectively.…”