Localization and nature of radiation donor defects in the arsenic implanted CdHgTe films grown by MBE

By profiling the electrical parameters of the arsenic implanted CdHgTe films, grown by molecular bea

Symmetry breaking and circular photogalvanic effect in epitaxial CdxHg1-xTe films

We report on the observation of symmetry breaking and the circular photogalvanic effect in CdxHg1-xTe alloys. We demonstrate that irradiation of bulk epitaxial films with circularly polarized terahertz radiation leads to the circular photogalvanic effect (CPGE) yielding a photocurrent whose direction reverses upon switching the photon helicity. This effect is forbidden in bulk zinc-blende crystals by symmetry arguments; therefore, its observation indicates either the symmetry reduction of bulk material or that the photocurrent is excited in the topological surface states formed in a material with low cadmium concentration. We show that the bulk states play a crucial role because the CPGE was also clearly detected in samples with noninverted band structure. We suggest that strain is a reason for the symmetry reduction. We develop a theory of the CPGE showing that the photocurrent results from the quantum interference of different pathways contributing to the free-carrier absorption (Drude-like) of monochromatic radiation

Electrical profiling of arsenic-implanted HgCdTe films performed with discrete mobility spectrum analysis

The results from the electrical profiling of an n-on-p junction formed by 190-keV arsenic ion implantation in an indium/vacancy–doped Hg0.78Cd0.22Te film are presented. Mobility spectrum analysis in combination with wet chemical etching has been employed for the profiling. After the implantation, a typical n + -n-р structure was observed and three electron species were detected: (a) low-mobility electrons in the 400–500 nm-thick top radiation-damaged n + -layer, (b) mid-mobility electrons also originating from radiation damage and spreading down to 700–900 nm, and (c) high-mobility electrons located in the n-region extending beyond 700–900 nm and down to the p-n junction. A comparison of the extracted electron parameters with the arsenic profile obtained with secondary-ion mass spectroscopy as well as with the defect pattern obtained with transmission electron microscopy allowed for the identification of the origin of all three electron species

Arsenic-ion implantation-induced defects in HgCdTe films studied with Hall-effect measurements and mobility spectrum analysis

The Hall-effect/electrical conductivity measurements and mobility spectrum analysis (MSA) have been used for the study of the profiles of different electron species and corresponding defects induced in a HgCdTe film by implantation of arsenic ions. Two specific donor defects were revealed as a result of extracting parameters of different carrier species found with MSA. Identification of the defects was performed with the use of the data acquired with transmission electron microscopy and the literature data on Rutherford backscattering. It was found that low-mobility (∼5000 cm2/(V·s)) electrons originated from donor centers formed when mercury interstitials were captured by implantation-induced dislocation loops, while middle-mobility (∼20,000 cm2/(V·s)) electrons were due to donor centers formed when the interstitials were captured by quasi-point radiation defects. For comparison, profiling was also performed with the single-field differential Hall-effect measurements. The results of the study suggest that only MSA-assisted carrier profiling is capable of retrieving actual defect profiles in ion-implanted HgCdTe