Improved control of composition and electrical properties of liquid phase epitaxial (CdHg)Te layers

The use of powdered HgTe as a source of mercury in a graphite sliding boat used for liquid phase epitaxial (LPE) growth of CdxHg1−xTe alloys from Te-rich solutions at 460°C has been found to give excellent reproducibility of alloy composition, x and thickness due to the low Hg loss rates during growth (typically 0.3 mg min-1). Reproducibility of the wavelength corresponding to an absorption coefficient, α, of 500 cm-1 (λα = 500) is ± 0.15 μm, while the thickness reproducibility is typically ± 1 μm for 20μm thick layers. The variation of composition with depth in the layers is typically (2–4)x10-4 in x per μm. Background carrier concentrations in undoped layers after Hg-rich annealing to remove Hg vacancies are n = (6–8)x1013 cm-3. Using SIMS analysis we have shown that In is 100% electrically active after Hg-rich annealing and that the In dopant does not diffuse during the anneal treatment. Copper (Cu) doping has been studied for p-type material in the range 8×1015 to 2×1018 cm-3. The Cu appears to be nearly 100% electrically active in as-grown layers, but during Hg-rich isothermal annealing at 250° C, a certain proportion of the Cu diffuses to the surface leaving only about 30% of the Cu in the bulk of the layer still electrically active

In situ ellipsometry studies of electrodeposited cadmium telluride films on cadmium mercury telluride

The electrodeposition of CdTe on CdxHg1-xTe is carried out from aqueous solutions at 55 degrees C and the film growth is monitored using in situ ellipsometry. The measurements reveal that, at a growth potential of -0.55 V versus SCE, a thin (120 AA) Te layer is initially formed on the surface followed by the growth of the CdTe film (1.8 mu m) which appears to be of uniform composition for most of its thickness. Further analysis of the film using the techniques of Raman spectroscopy, differential scanning calorimetry (DSC) and energy dispersive X-ray analysis (EDAX) confirm the excess tellurium in the electrodeposited film. The EDAX measurements after electrodeposition also reveal the presence of 2-8% Hg in the film depending on the depth of analysis. The presence of Hg in the film can only be explained by the diffusion of Hg from the substrate through the electrodeposited layer

In situ ellipsometry studies of electrodeposited cadmium telluride films on cadmium mercury telluride

The electrodeposition of CdTe on CdxHg1-xTe is carried out from aqueous solutions at 55 degrees C and the film growth is monitored using in situ ellipsometry. The measurements reveal that, at a growth potential of -0.55 V versus SCE, a thin (120 AA) Te layer is initially formed on the surface followed by the growth of the CdTe film (1.8 mu m) which appears to be of uniform composition for most of its thickness. Further analysis of the film using the techniques of Raman spectroscopy, differential scanning calorimetry (DSC) and energy dispersive X-ray analysis (EDAX) confirm the excess tellurium in the electrodeposited film. The EDAX measurements after electrodeposition also reveal the presence of 2-8% Hg in the film depending on the depth of analysis. The presence of Hg in the film can only be explained by the diffusion of Hg from the substrate through the electrodeposited layer

In situ ellipsometry studies of electrodeposited cadmium telluride films on cadmium mercury telluride

The electrodeposition of CdTe on CdxHg1-xTe is carried out from aqueous solutions at 55 degrees C and the film growth is monitored using in situ ellipsometry. The measurements reveal that, at a growth potential of -0.55 V versus SCE, a thin (120 AA) Te layer is initially formed on the surface followed by the growth of the CdTe film (1.8 mu m) which appears to be of uniform composition for most of its thickness. Further analysis of the film using the techniques of Raman spectroscopy, differential scanning calorimetry (DSC) and energy dispersive X-ray analysis (EDAX) confirm the excess tellurium in the electrodeposited film. The EDAX measurements after electrodeposition also reveal the presence of 2-8% Hg in the film depending on the depth of analysis. The presence of Hg in the film can only be explained by the diffusion of Hg from the substrate through the electrodeposited layer