M. Pociask

Conductivity type conversion in ion-milled p-HgCdTe:As heterostructures grown by molecular beam epitaxy

Conductivity type conversion in ion-milled As-doped p-HgCdTe heterostructures grown by molecular beam epitaxy on GaAs substrates has been studied. It was found that in these heterostructures, donor center concentration (∼1017cm−3) after ion milling was much higher than that could have been expected as a result of interaction of interstitial mercury atoms, generated under the milling, with the As acceptors. One possible reason of the donor center formation is the activation of an intrinsic neutral defect, which was present in the HgCdTe:As prior to the ion milling. The nature of the donor centers formed is discussed.

Ion milling-induced conductivity-type conversion in p-type HgCdTe MBE-grown films with graded-gap surface layers

In this paper, ion milling-induced conductivity-type conversion in p-type HgCdTe molecular beam epitaxy-grown films with graded-gap surface layers is studied. As expected, the chemical composition of the graded-gap layer strongly affects the conversion depth. At the composition of the layer on the surface, xv > 0.5, ion fluences typically used for fabricating p?n junctions in HgCdTe create only a damaged surface n+-layer with no deep conversion. With lower xv, conversion with controllable depth due to diffusion of interstitial mercury atoms HgI can be achieved. Defect reactions in the graded-gap surface layers under the milling and post-milling ageing, which are caused by interaction of HgI with dislocations, differ from those in the deep converted layers, where HgI reacts with point defects. It is shown that when assessing the depth of a p?n junction fabricated with ion milling in HgCdTe with a graded-gap surface layer, it is necessary to consider the effect of the material removal from the surface.

Electrical properties of n-HgCdTe heteroepitaxial layers modified by ion etching

Electrical properties of MBE-grown n-HgCdTe layers, both undoped and In-doped during growth and modified by ion etching are studied. It is established that initially neutral defects with a concentration ∼1017 cm−3 are present in these structures. These defects are activated by ion etching and form donor centers. Comparison of the obtained experimental results with the published data shows that these defects are formed at the growth stage of the structures. After the ion etching is stopped, donor centers decompose and for ∼5 × 103 min, the electron concentration in the structures is stabilized. The obtained data allow one to determine the amount of indium necessary for the obtainment of reproducible electron concentration in n-type regions of HgCdTe-based LED structures formed by ion etching.

Relaxation of electrical properties of epitaxial Cd x Hg 1-x Te:As(Sb) layers converted into n-type by ion milling

Results of the studies of relaxation of electhcal properties of As- and Sb-doped CdxHg1-xTe epitaxial layers, which were converted into n-type by ion milling (TM), are presented. It is demonstrated that donor complexes, which are formed under IM and are responsible for p-to-n conductivity type conversion, are not stable, and their concentration decreases upon storage even at the room temperature. The relaxation at room temperature results in electron concentration in converted layers decreasing from the initial value of ~(2-3)x 1015 cm right after the milling down to the value of ~l015 cm-3. Increasing the temperature of the storage speeds up the relaxation. The process responsible for the relaxation appeared to be the disintegration of the donor complexes, which starts after the end of the IM and is caused by the decrease in concentration of interstitial mercury atoms, generated by milling.