Nanooptics and photonics

Unipolar superlattice structures based on MBE HgCdTe for infrared detection
Izhnin I.I.1, Kurbanov K.R.2, Voitsekhovskii A.V.3, Nesmelov S.N.3, Dzyadukh S.M.3, Dvoretsky S.A.3,4, Mikhailov N.N.4, Sidorov G.Yu.4
1 Scientific Research Company “Electron-Carat”, Stryjska St., 202, Lviv 79031,Ukraine E-mail: i.izhnin@carat.electron.ua
2Kremenchug Flight College, Pobedy St., 17, Kremenchug, 39600, Ukraine
3 Tomsk State University, Lenina Av., 36, Tomsk 634050, Russia
4 A.V. Rzhanov Institute of Semiconductor Physics of SB RAS, Lavrent’ev Av., 13, Novosibirsk, 630090, Russia.

A new approach to creating high-temperature infrared detectors based on HgCdTe grown by molecular beam epitaxy (MBE) is the use of unipolar nBn architecture [1]. The use of the HgCdTe/CdTe superlattice as the barrier layer instead of the wide-gap layer allows one to improve the photosensitivity of the detectors by reducing the potential barrier for holes. The work presents the results of studying the dark and signal characteristics of MWIR nBn structures based on MBE n-HgCdTe with a different design of the barrier layer.
Structures for studies were made by molecular beam epitaxy on GaAs(013) substrates. For samples of type 1, the barrier layer was created from wide-gap MBE Hg1-xCdxTe (x=0.66-0.83), and for type 2 structures, a superlattice of 18 periods Hg0.20Cd0.80Te (9 nm) - HgTe (2 nm) was used as a barrier layer. Current-voltage characteristics (CVCs) of nBn structures of various types were studied in a wide range of temperatures (8-300 K) in the dark and under illumination. The dark current density at reverse bias for such structures turned out to be significantly less than the current density for structures described in the literature [1]. Investigations of the CVCs for various areas of device structures made it possible to study the role of surface leakage currents. For nBn structures with a superlattice (type 2 samples), the current density increases with reverse bias, which indicates a decrease in the height of the potential barrier for holes. The mechanisms of formation of the characteristics of the studied nBn structures are discussed.

1.	Istuno A. M., Phillips J. D., Velicu S. Mid-wave infrared HgCdTe nBn photodetector // Appl. Phys. Lett.-2012.-100.-P. 161102 (1-3).