Microscopic Defects and Infrared Absorption in Cadmium Telluride

Abstract

The correlation observed in CdTe between microscopic defects and the infrared absorption at 10.6 μm is reported. The data were obtained from transmission electron microscopy, scanning electron microscopy, infrared and optical microscopy, spectrophotometry, and laser calorimetry. For chlorine and indium doped samples it was determined that increasing the concentrations of In2Te3 and CdCl2 precipitate platelets subsequently increases the 10.6 μm infrared absorption coefficient in CdTe. Isolated dislocations, dislocation networks, tellurium precipitates, vacancy loops, and stacking faults were also shown to exercise an important influence on infrared absorption. Localized regions of defect aggregations in many samples were found to be responsible for the macroscopicabsorption sites typically observed by infrared microscopy. The significant differences between the present data and previously reported macroscopic defect models are discussed.

A multi-technique characterization of electroless gold contacts on single crystal CdZnTe radiation detectors

“…This was attributed to the preferential removal of cadmium by the gold chloride solution and subsequent precipitation of cadmium chloride due to supersaturation of the Cd 2+ and Cl − containing solution. The precipitation of CdCl 2 will reduce the crystal quality and increase voiding [33][34][35][36] due to the solubility of chloride salts and sub-surface stress from lattice mismatches causing strain and local deformations. The bright regions observed in the bright field image of figure 4 were consistent with porosity or voiding.…”

“…The cadmium peak is known to shift to higher binding energies when bound with Cl [20,43]. The ratio of the second cadmium PCA component (Cd PCA2) to chlorine (Cl 2p) was found to be ∼1 : 1 throughout the profile suggesting a phase of CdCl, although CdCl 2 could have formed [33][34][35][36] with the ratio distorted by preferential etching. The position (405.0 eV) and distribution of the first cadmium component (Cd PCA1) was consistent with cadmium bound as CdZnTe.…”

Basic principles of postgrowth annealing of CdTe:Cl ingot to obtain semi-insulating crystals

“…, the minimal value necessary for crystal self-compensation to occur in CdTe growth from the melt [14], to N(Cl) = 2x10 19 cm -3 , at which CdCl 2 precipitates at the grain boundaries [15]. To .…”

Characterization of the metal–semiconductor interface of gold contacts on CdZnTe formed by electroless deposition

“…The precipitation of CdCl 2 within the interface occurs during electroless deposition as the concentration of Cd 2+ and Cl − reach supersaturation levels within the solution. Chloride species have previously been observed in the interface following electroless deposition [50][51][52][53] and PCA analysis of XPS measurements [41] have confirmed that the depth distribution of metal chloride correlates with that of a compound of cadmium other than CdZnTe.…”

“…The current FIB images show subsurface voids in the CdZnTe crystal below the contact. The presence of voids and degradation of crystal quality has been attributed to the precipitation of CdCl 2 [50][51][52][53]. Voids and local deformations form due to stress from lattice mismatches and the solubility of chloride salts.…”