Abstract
In this paper we present the status of HgCdTe barrier detectors with an emphasis on technological progress in metalorganic chemical vapor deposition (MOCVD) growth achieved recently at the Institute of Applied Physics, Military University of Technology. It is shown that MOCVD technology is an excellent tool for HgCdTe barrier architecture growth with a wide range of composition, donor/acceptor doping, and without post-grown annealing. The device concept of a specific barrier bandgap architecture integrated with Auger-suppression is as a good solution for high-operating temperature infrared detectors. Analyzed devices show a high performance comparable with the state-of-the-art of HgCdTe photodiodes. Dark current densities are close to the values given by “Rule 07” and detectivities of non-immersed detectors are close to the value marked for HgCdTe photodiodes. Experimental data of long-wavelength infrared detector structures were confirmed by numerical simulations obtained by a commercially available software APSYS platform. A detailed analysis applied to explain dark current plots was made, taking into account Shockley–Read–Hall, Auger, and tunneling currents.
Highlights
At present, one of the leading topics in highoperating temperature (HOT) infrared (IR) detectors are barrier devices, including nBn and pBn design.[1,2,3,4] Barrier detectors in such configuration require a proper bandgap engineering
This paper presents the status of metalorganic chemical vapor deposition (MOCVD)-grown HgCdTe barrier detectors, with emphasis on technological achievements in removing the valence band offset made recently at the Institute of Applied Physics, Military University of Technology (MUT).[17,18,19]
Barrier detectors presented in this paper were optimized at 50% cut-off wavelengths up to 3.6 lm, 6 lm, and 9 lm at 230 K
Summary
One of the leading topics in highoperating temperature (HOT) infrared (IR) detectors are barrier devices, including nBn and pBn design.[1,2,3,4] Barrier detectors in such configuration require a proper bandgap engineering. Non-zero valence band offset in HgCdTe nBn detector structures is the key item limiting their performance.[6,7,8,9,10,11] Devices exhibit poor responsivity and detectivity, especially at low temperatures,[6] where the low-energy minority carriers generated by optical absorption are not able to overcome the valence band energy barrier (DEV) (see Fig. 1a). Devices presented within the framework of this paper have a p+-Bp cap-barrier structural unit, intentionally undoped (due to donor background concentration with n-type conductivity) or a low ptype doped absorption layer and wide band-gap highly doped N+ bottom contact layer.
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