Hg_1-xCd_xTe doping by ion-beam treatment

Abstract

Conductivity-type conversion and modification of the electrical properties of p and n-type Hgl,CdxTe epitaxial layers subjected to low energy (1.2-1.8 kev) ion-beam treatment have been investigated. The dependence of the conversion depth on the treatment parameters and the material characteristics has been studied. Chemical diffusion of mercury has proved to be the principal process that determines the conversion rate. The electron concentration in the treated Hgl, Cd. , Te samples is found to be determined by the werall concentration of the background donor impurities and native donor defects. The latter seem to be generated during the postgrowth thermal annealing.

Properties of MBE Cd x Hg 1− x Te/GaAs structures modified by ion‐beam milling

“…1. It can be seen that the electron-concentration and mobility distributions over the investigated MBE Cd x Hg 1-x Te sample are similar to those for bulk homogeneous n-Cd x Hg 1-x Te layers modified by IM [3]. Namely, in a thin subsurface (damaged) layer (∼2 µm) the electron concentration falls from surface to sample depth and further, in the main part of the n-type layer, has a constant value.…”

“…This shows that the filling of Hg vacancies in this region during conversion is limited by the rate of supply of extra Hg due to the milling process. It corresponds to the results [1,9] but it is opposite to the conclusions of [3,4,10]. Besides, in [8] any dependence of conversion depth on Cd content in active MCT layers was not observed and this does not match experimental results [11] and theoretical predictions [10].…”

“…But the thickness of the converted layers was much smaller than had been predicted by theory [10] and that experimentally observed in [3,4] for uniform bulk Cd x Hg 1-x Te samples with the same acceptor concentration and IM conditions. It is presumed that these distinctions are due to the presence of the wide band gap gradient surface layer, which results in decreasing of the conversion rate because of the internal electric field action [10].…”

“…This definitely indicates a diffusion-like process of conversion front movement in samples (see [3,4,10]). But the thickness of the converted layers was much smaller than had been predicted by theory [10] and that experimentally observed in [3,4] for uniform bulk Cd x Hg 1-x Te samples with the same acceptor concentration and IM conditions.…”

Study of the Defect Structure of Hg1-xCdxTe Films by Ion Milling

“…This effect is now widely used in MCT technology, when ion milling is employed for fabrication of p−n junctions in vacancy-and acceptor-doped-type material. It appeared also that strongly non-equilibrium processes which take place under ion milling, when a crystal is oversaturated with interstitial mercury atoms Hg I [2,3], allowed one to detect defects that did not show their presence before the milling because of electrical compensation [4,5]. The character of post-milling relaxation of electrical properties of MCT allows for identifying background dopants, which are hard to detect using secondary-ion mass-spectroscopy (SIMS) [6].…”