Impedance of MIS devices based on nBn structures from mercury cadmium telluride

Three types of nBn structures based on mercury cadmium telluride grown by molecular beam epitaxy were fabricated. As the barrier layers in nBn structures, we used Hg_{1- x} Cd _x Te at x = 0.67 and 0.84, as well as a superlattice of 18 periods Hg_0.20Cd_0.80Te (9 nm) - HgTe (2 nm). To study the properties of barrier layers based on nBn structures, MIS devices were created using dielectric Al₂O₃ films. The impedance of the formed devices is studied in a wide range of voltages, frequencies, and temperatures. Equivalent circuits of MIS devices based on nBn structures in the accumulation mode are proposed. It is shown that measurements of the frequency dependences of the impedance make it possible to determine the differential resistance of the barrier layer in a wide range of conditions. It was established that the determined values of the differential resistance are determined only by the bulk component of the dark current, and the surface leakage component does not affect the measured impedance of MIS devices. The dependences of the values of the elements of the equivalent circuit on the area of structures, on voltage and temperature are determined. It is shown that the differential resistance of the barrier layer based on Hg_0.33Cd_0.67Te in the temperature range 210-300 K at forward biases is determined by the diffusion-limited flow of holes from the contact layer, and at reverse biases, from the absorbing layer. The values of the product of differential resistance by area for nBn structures with different parameters of the barrier layers are determined. The possibilities of using impedance measurements of MIS devices based on nBn structures to study the uniformity of the properties of various layers are demonstrated.

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