In-situ p-type doping activation near the MBE growth temperature of HgCdTe for advanced LWIR detectors
Agency / Branch:
DOD / USAF
High-performance HgCdTe infrared focal plane arrays (IRFPAs) sensing in the long-wavelength infrared (LWIR) region and advanced structures such as multi-color detectors required for future generation IRFPAs are highly desirable for various Air Forceapplications. Such device architectures require not only reliable extrinsic n- and p-type doping of HgCdTe but also the precise control of composition and doping profiles. This can be best achieved using Molecular Beam Epitaxy (MBE) within a single growthrun for a specific architecture. Although n-type doping with indium is well under control in MBE-HgCdTe, the situation concerning p-type doping with arsenic, which is the most suitable acceptor, is not satisfactory. In current technology, a hightemperature anneal above 400¿C is necessary to activate the arsenic species into acceptors. It is mandatory to develop a viable, reproducible and effective p-doping approach that does not involve thermal treatments above 250¿C in order to preserve thecompositional and doping profile integrity of HgCdTe-based structures. In Phase I, we demonstrated that in-situ As-doped MWIR HgCdTe can be p-type activated after a thermal anneal at 250¿C through a proprietary two-step process. In Phase II, we propose tooptimize this process by a precise control of arsenic incorporation and site transfer. The assessment of success will be established through the device processing and testing of p/n and n/p heterostructures with the goal of exceeding the reportedperformance of LWIR ion implanted structures.
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