Electrical properties of langmuir-blodgett passivation film for hg_1-x cd_xte

The electrical properties of the metal insulator semiconductor (MIS) structure of Hg_1-xCd_xTe (MCT, _x = 0.2 and 0.3) passivated by Langmuir-Blodgett (LB) films have been investigated. The insulation film is formed by photo-polymerized LB films of 10, 12-heptacosadiynoic acid on an electrochemically reduced MCT surface. From the linear dependence of the reciprocal capacitance on the amount of LB films, the dielectric constant of the LB film is evaluated to be 2.95. The dispersion of capacitance under the accumulation condition is very small in the frequency range between 1 kHz and 2 MHz. The surface on n-Hgo.7Cdo.3Te is slightly accumulated at zero bias and has a surface state density of 2 x 10¹¹ cm^-2 eV^-1 at the midgap. On the other hand, that of p-Hg_0.7Cd_0.3Te is slightly depleted and has a surface state density of less than 1 x 1011 cm^-2 eV^-1. The small hystereses in flatband voltage are 0.001 V and 0.02 V, corresponding to trap densities of 1.1 x 10⁸ cm-2 and 1.7 x 10⁹ cm^-2 for n-and p-Hg_0.7Cd_0.3Te, respectively.