HgCdTe Structures for Dual-Band Photodetectors Operating in the 3–5 and 8–12 µm Spectral Ranges
V. S. Varavin, S. A. Dvoretskii, D. G. Ikusov, N. N. Mikhailov, V. G. Remesnik, G. Yu. Sidorov, Yu. G. Sidorov, P. N. Sizikov, I. N. Uzhakov
Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent’eva 13, Novosibirsk, 630090 Russia
Keywords: cadmium–mercury–tellurium, molecular beam epitaxy, infrared photodetectors
Abstract
A bilayer cadmium–mercury–tellurium (CMT) heterostructure was designed consisting of photosensitive layers of compositions xCdTe = 0.29–0.32 and xCdTe = 0.220–0.230, sensitive in the spectral ranges of 3–5 and 8–12 µm, a barrier layer between them, and wide-band variable-gap layers on the heterojunction and the surface grown on a GaAs substrate with ZnTe and CdTe buffer layers. The molecular beam epitaxial (MBE) growth of the heteroepitaxial structure (HES) was controlled by real time ellipsometry. After the growth, the composition distribution throughout the thickness was measured by reflection spectra with layer-by-layer chemical etching. There is good agreement between the results of composition measurements using ellipsometry and reflection spectra. P-type conductivity of bilayer MBE CMT HESs was obtained after thermal annealing at 220–240 ºC in an inert gas (helium) for 24 h. The concentration of holes in the photosensitive layers is (4–10) ·1015 cm−3 and (8–20) · 1015 cm−3 at 78 K.
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