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

Abstract

The results from the electrical profiling of an n-on-p junction formed by 190-keV arsenic ion implantation in an indium/vacancy-doped Hg 0.78 Cd 0.22 Te 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) midmobility 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.

Electrical and microscopic characterization of p+-type layers formed in HgCdTe by arsenic implantation

“…A disappeared, while the dislocation loops transformed into single dislocations with a higher density (an upper layer B 1 ' with thickness ∼ 120 nm) and a lower density (a lower layer B 2 ' with thickness ∼ 170 nm). The results of the TEM studies clearly confirm partial annealing of defects that are known to capture Hg I and provide n-type conductivity in as-implanted MCT [12].…”

“…The details of the extraction of carrier parameters from the mobility spectra were given in Ref. [12] on the example of arsenic-implanted n + -on-p MCT structures. Figure 2 shows the transformation of primary mobility spectrum envelopes (MSEs) calculated according to the standard MSA algorithm developed by Beck and Anderson [18] for samples F2 and F3.…”

“…Their concentration in the ∼350 nm thick implanted layer equalled ∼4.6 × 10 17 cm -3 . This suggests that in both n-and p-type implanted MCT the lowmobility electrons originate in interstitial mercury (Hg I ) atoms captured by the dislocation loops [12] and the conductivity type of the initial material does not affect the process of the formation of implantation-induced defects.…”

“…Thin foils for the studies were cut out using FEI Quanta 200 dual-beam focused-ion (Ga + ) beam machine equipped with an OmniprobeTM lift-out system. The Halleffect studies involved the measurements of the magnetic field B dependences of the Hall coefficient R H and the conductivity σ in the fields B = 0.01-1.5 T at T = 77 K. The data of these measurements were analyzed with the use of the discrete mobility spectrum analysis (DMSA) [11,12]. This technique allows one to determine the number of carrier species and the numerical values of their parameters: average concentration, mobility and partial conductivity.…”

“…The analysis of the behaviour of the mid-mobility electrons was more challenging to perform. These electrons were found in both the as-grown samples (where they could be related to the transitional substrate/film buffer layer [19,20]), and in the as-implanted samples, where they could result from the formation of the implantation-induced quasi-point defects, which capture Hg I [12]. Straight after the implantation the concentration of these electrons was two times higher than that in the as-grown samples, but the exact contributions by the two sorts of these carriers could not be resolved.…”