We report fast and sensitive long (10 μm) wavelength photodetectors operating at near room temperature. The
devices are based on HgCdTe multilayer heterostructures grown by MOCVD on (211) and (111) GaAs substrates.
Device-quality heterostructures are obtained without any post growth anneal. The recent improvements of MOCVD
growth were: optimized design of the device architecture to increase speed of response, better IMP growth
parameters selection taking into account interdiffusion time changes during growth, stoichiometry control during
growth by the layer anneal at metal rich vapors during each IMP cycle, precursor delivery to the growth zone
monitored with IR gas analyzer, additional metal-rich vapor anneal at the end of growth and passivation of detector
structures with wide gap HgCdTe overgrowth deposition. Monolithic optical immersion of the detectors to GaAs
microlenses has been applied in purpose to improve performance and reduce RC time constant. The response time of
the devices have been characterized using 10μm quantum cascade laser, fast oscilloscope with suitable
transimpedance amplifier as a function of detector design, temperature and bias. Detectivity of the best
thermoelectrically cooled optically immersed photodiodes approaches 1⋅1010 cmHz1/2/W at ≈10 μm wavelength. The
response time of small area decreases with reverse bias to response achieving <100 ps with weak reverse bias.
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