Inexpensive high-performance large-format imaging sensors are highly needed for the next generation of the Army’s persistent surveillance applications. Sb-based Type-II superlattices (T2SLs) represent the most promising material system capable of delivering a more manufacturable and affordable large-format focal plane array technology than the current technology, while at the same time exhibiting similar or better performance. Improvement in material quality and processing technique, as well as evolutionary modifications in device architecture have demonstrated the advantages of this material system over alternatives, and proven it as a viable candidate for the next generation infrared imaging. Despite this rapid development, it still suffers from a relatively high cost mainly associated with its growth method. Until now, most of the T2SLs structures and devices have been grown by molecular beam epitaxy (MBE), which is expensive for mass production application. For this reason, there is a much interest in growing T2SLs by metal-organic chemical vapor deposition (MOCVD), which could enable lower-cost and versatile production. Growth of high quality Sb-based materials by MOCVD is more challenging than by MBE due to the fundamental properties of Sb such as low melting points, low equilibrium vapor pressure and lack of stable hydride of Sb. During the growth of T2SLs structures by MBE, InSb-type of interfacial layer is usually employed to effectively balance the tensile strain. However, this approach is not useful for the MOCVD growth of InAs/GaSb SLs due to the low melting temperature of InSb. During MOCVD growth, both the group III and group V precursor decomposition efficiency increases with increase of the growth temperature. Therefore, the typical growth temperatures used in MOCVD are close to or even higher than the melting point of InSb in order to have reasonable decomposition efficiency of the precursors. During this project, we propose to study metal-organic chemical vapor deposition (MOCVD) growth of strain-balanced InAs/InAs1-xSbx T2SLs for LWIR detection and imaging. Compared to the complex interfacial schemes during the growth of InAs/GaSb T2SLs, InAs/InAs1-xSbx T2SLs can be grown on GaSb substrate in a strain balanced manner. InAs/InAs1-xSbx T2SLs has relatively simple interface structure with only one changing element (Sb), which reduces the complexity of interface control during growth. Furthermore, InAs/InAs1-xSbx T2SLs has been proven to have longer minority carrier lifetime, which results in lower dark current, higher operation temperature, and higher quantum efficiency. Combined with MOCVD growth and this Type-II superlattice design, it is expected to achieve low cost, high performance and large format imaging sensors. In this effort, new barrier structure will also be investigated for barrier infrared detector development. Typically, AlSb-based SLs structures are used for barrier structure, which could offer a very high band gap and a relatively small lattice mismatch with GaSb substrate. However, MOCVD growth of AlSb-compound is more difficult due to the lack of suitable sources for the growth of AlSb at low temperatures and resulting incorporation of excess smounts of carbon. In order to address this challenge, novel barrier structure based on GayIn1-yAs1-xSbx quaternary alloy and GayIn1-yAs/InAs1-xSbx T2SLs will be investigated. k·p model as well as the Empirical Tight Binding Model (ETBM) will be used for theoretical barrier structure design. Systematic optimization of MOCVD growth of barrier structure will
|Effective start/end date||8/2/18 → 6/1/22|
- Army Research Office (W911NF1810402-P00004)
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