Two types of long-wave infrared nBn structures based on mercury cadmium telluride grown by molecular beam epitaxy on GaAs (013) substrates have been fabricated. For each type of device, the side walls of the mesa structures were passivated with an Al2O3 dielectric film or left without passivation. The CdTe content in the absorbing layers was 0.20 and 0.21, and in the barrier layers, 0.61 and 0.63. The dark currents of the manufactured devices were studied in a wide range of voltages and temperatures. The values of the surface leakage component are found under various conditions. It has been shown that the surface leakage current density decreases upon passivation with an Al2O3 film. It was found that at room temperature in the fabricated nBn structures with reverse biases, the surface leakage component dominates, and with forward biases, the dark current is determined by the combined effect of the surface leakage component and the bulk current component. From the Arrhenius plots, the values of the activation energies of the surface leakage current component were found, which at small reverse biases are in the range from 0.05 to 0.10 eV. At small reverse biases, upon cooling the samples, the role of the bulk component of the dark current increases, which at 180 K is approximately 0.81 A/cm2. In the temperature range 200-300 K, the values of the dark current density exceed the values calculated according to the empirical Rule07 model by a factor of 10-100, which indicates the possibility of creating long-wave infrared barrier detectors with a decrease in the values of the surface leakage component.