Application of CdTe epitaxial layers for passivation of p-type Hg _0.77Cd_0.23Te

We have investigated the properties of CdTe/Hg_0.77Cd _0.23Te heterostructures in order to evaluate the use of thin CdTe cap layers for passivation of the HgCdTe surfaces. The energy band diagram across the interface of this structure was calculated using Anderson's model. It is found that flat or near flat band conditions can be obtained by using p-type CdTe with carrier density in the range of 10¹⁴-10¹⁵ cm^-3. CdTe/Hg_0.77Cd_0.23Te heterostructures were grown on CdTe (211)B oriented substrates using the metalorganic chemical vapor deposition technique. The interface properties of CdTe/HgCdTe were investigated by a combination of Hall and photoelectromagnetic effect measurements as a function of temperature, magnetic field, and light illumination wavelength. Interface recombination velocities of less than 5000 cm/s were obtained at 77 K for heterostructures grown under proper conditions. These values are more than two orders of magnitude lower than those obtained for freshly Br:methanol etched HgCdTe surfaces. These results demonstrate that CdTe cap layers may be used as a good passivation of HgCdTe surfaces.