Interfacial Misfit Dislocation Array based Metamorphic Antimonide Buffers for LWIR Detectors
Abstract
The objective of the proposal is to realize efficient LWIR detectors in the wavelength range of 8 - 13 ?m Êbased on using InAsSb ( absorbers grown on metamorphic 6.27 � lattice constant buffers on GaAs, InP and Silicon substrates. With recent demonstrations of near-minimum bandgap (0.1?eV) bulk InAs0.54Sb0.46 on GaAs, the limiting factor in achieving high performance LWIR detectors on GaAs, Silicon or other commercially viable substrates has been the ability to realize low threading dislocation density metamorphic buffers. The proposal makes use of two key innovations in buffer technology to realize such a platform. The first technology is the realization of novel interfacial misfit dislocation (IMF) layers grown on InP and GaAs substrates that will allow for the access of lattice constants at ~ 6.27 � on these platforms. The idea behind these IMF layers is to grow InGaSb on InGaAs/InP and InGaSb on InGaP/GaAs. In both these cases the top group V layer in the ternary layer is replaced with an Sb layer using conditions that promote interfacial misfit dislocations, which involves realizing specific multilayer Sb surface reconstructions. In the case of InGaSb/InGaAs/InP structures we have observed strong photoluminescence from the buffer at room temperature indicating a high quality buffer layer. An added benefit of these IMF layers is the excellent etch contrast between the antimonide and the arsenide or phosphide layers that allows from complete epitaxial lift off from the underlying substrate. Thus the project will allow for the realization of a fully relaxed epitaxial detector structure with a lattice constant of 6.27 - 6.28 �, with the ability to be fully integrated with read out integrated circuits (ROICs). The second buffer technology is the incorporation of highly optimized defect filter layers that will achieve further reduction in the threading dislocation density allowing for reduced reverse bias leakage in such detectors. The optimization of the defect filter layer is based on a transmission electron microscopy technique developed at UNM which allows for the physical extraction of a defect filter layer using focused ion beam milling to observe the threading dislocation network in the membrane. The presence of complex threading dislocations interacting on such a filter layer has been shown to correlate to a reduced threading dislocation density in the materials. The ability to relate the presence of dislocation networks to the threading dislocation annihilation process has resulted in an order of magnitude reduction in threading dislocation density in the diode structure. Finally the proposal will include the growth of the detector structures on Silicon substrates. The growth of the IMF layer on Silicon will require direct growth of the final InGaSb composition onto the silicon layer with an intermediate AlSb layer. The AlSb layer will facilitate the formation of the IMF interface. The project will include extensive growths of the buffers and the subsequent detectors using Molecular Beam Epitaxy. The initial year of the project will focus on the optimization of the buffers and on reduction of the threading dislocation density in the epitaxial material. The realization of the new IMF layers and the optimization of the threading dislocation blocking layers will involve growth followed by extensive characterization using transmission electron microscopy. The second and third year of the project will include the fabrication of InAsSb detectors on three platforms - GaAs, InP and Silicon.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 24, 2019
- Source ID
- W911NF1910370
Entities
People
- Ganesh Balakrishnan
Organizations
- Army Contracting Command
- United States Army
- University of New Mexico