Investigation of the bulk and surface electronic properties of HgCdTe epitaxial layers using photoelectromagnetic, Hall, and photoconductivity measurements

In this work a method is presented that permits the evaluation of the bulk and surface electronic properties of p-type Hg_0.77Cd_0.23Te epilayers grown by metalorganic chemical-vapor-deposition and liquid-phase-epitaxy growth techniques. The method is based on fitting the generalized photoelectromagnetic expression to the experimental results obtained from photoelectromagnetic, Hall, and photoconductivity measurements. Values of electron mobility, electron diffusion length, bulk lifetime, surface recombination velocities at the front and at the back surfaces of the HgCdTe layer, and the absorption coefficient were derived as a function of temperature. It is found that the Shockley-Read-Hall recombination process is the dominant recombination mechanism both in the bulk and at the surface of the HgCdTe layers. The recombination centers are most likely related to metal vacancies. It is shown that a low value of surface recombination velocity is a fundamental property of the CdTe/HgCdTe interface. In particular, a surface recombination velocity of less than 5000 cm/s was measured at 77 K for HgCdTe with a CdTe cap, which is the lowest value reported for narrow-gap p-type HgCdTe.