Magneto-Optical Properties of a Hydrogen-Related Defect in CdTe

Abstract

Nominally undoped CdTe was exposed to a hydrogen plasma at 160 C. It has been shown that after this treatment, seven typical photoluminescence lines H 1 to H 7 are observed in the excitonic region. The dependence of the most intense of these hydrogen-related lines, H 3 , on external magnetic fields up to |B| = 7 T is investigated. The diamagnetic shift of the H 3 line is proportional to |B| 2 , showing that it is caused by the recombination of excitons. Since an electron±hole interaction is observed, the exciton is either bound to an isoelectronic defect or to an ionised donor. The anisotropy of the Zeeman splitting is explained in terms of a small uniaxial compressive strain in a [100] direction perpendicular to the [001] surface orientation. In contrast, the well-known copperbound exciton line, used as a reference, reveals uniaxial tensile strain in the same [100] direction. Therefore, the defects associated with the H 3 line either have a [100] symmetry or are incorporated close to [100] oriented extended defects. The electron g-factor is g e = ± ±1.50 AE 0.04, and the hole parameters are K = 0.40 AE 0.05 and L = 0.00 AE 0.04, describing the isotropic and the anisotropic Zeeman effect, respectively.Introduction. It has recently been shown that after the exposure of undoped CdTe to a hydrogen plasma at 160 C, seven new photoluminescence (PL) lines H 1 to H 7 are observed in the energy range between 1.575 and 1.591 eV. Since these lines are also visible after a 200 eV implantation of H + ions into CdTe, it was concluded that they are caused by the presence of hydrogen in CdTe [1,2]. High magnetic fields are a proper tool to investigate the electronic and microscopic structure of the associated defects. Only the H 1 , H 2 , and H 3 lines, however, are well isolated from each other and from other lines, which is favourable for magneto-optical investigations. In this paper, the results obtained from the H 3 line are presented, because this is the most intense line and thus yields the most reliable data. From the Zeeman splittings of the H 1 and H 2 lines, though not identical, similar conclusions can be drawn as for the H 3 line.Experimental Procedure. Nominally undoped, Bridgman-grown CdTe crystals were exposed to a hydrogen plasma at 160 C and 70 Pa for 1 h [1, 2]. The magneto-optical investigations were carried out at 1.7 K. The luminescence, excited by an Ar laser, was dispersed by a grating monochromator with a focal length of 1 m and detected by a 1 Corresponding