Indentation-introduced dislocation rosettes and their effects on the carrier transport properties of CdZnTe crystal

Abstract

Herein, we study the crystallographic configuration of rosette-like dislocation clusters introduced by indentation in CdZnTe (CZT) crystal and the effects of the dislocations on the carrier transport process. The Vickers hardness test was used to generate dislocations artificially on the (111) Te face of the CZT crystal at room temperature. Etch pit density (EPD) revealed by Everson etchant showed that the dislocation density increased from 4.9 × 10 4 cm −2 to a concentration too high to be evaluated after the indentation. A model was proposed to explain the rosette-like dislocation clusters. It was verified that the tetrahedron with small size and high EPD belonged to Te(g) dislocations on the (111) Te face. The hexagon-like distribution of pile-ups formed during the indentation was determined by the zinc-blende structure of CZT, rather than the direction of the indenter. The dislocation pile-up during propagation was observed and analyzed based on the rule proposed by Lomer and Cottrell. The ion beam induced charge (IBIC) measurements showed low carrier collection efficiency (CCE) in the dislocation generation areas, which confirms that the dislocations and related defects can significantly degrade the CCE of a CZT detector. Measurements of low temperature photo-luminescence (PL) showed that the emission peak located at 1.485 eV highly increased in the indentation area and was responsible for the performance degradation of the detectors. CrystEngCommThis journal is

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“…This band gap is sufficiently wide to inhibit the formation of thermally activated midgap carriers yet remains small enough to ensure high photoinduced carriers. − In addition, this material is very robust in mechanical properties, as shown from the Vickers hardness measurement (SI, Figure S2). Its Vickers hardness was estimated to be around 63 kg·mm –2 , which is comparable to that (73 kg·mm –2 ) of the commercial semiconductor detector material CZT …”

“…Its Vickers hardness was estimated to be around 63 kg• mm −2 , which is comparable to that (73 kg•mm −2 ) of the commercial semiconductor detector material CZT. 38 Photoluminescence. To identify the underlying radiative recombination mechanisms and to evaluate the crystal quality, Figure 3a shows a representative PL spectrum from a Tl 6 SI 4 single crystal under the laser intensity of 1000 mW•cm −2 at 17 K. The PL spectrum showed a broad emission band centered at 1.6 eV, consistent with the previously reported result on this compound by our group, while showing a much narrower fwhm (an fwhm value of ∼0.15 eV compared to the previously reported value of ∼0.18 eV).…”

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“…[9,10] The low charge collection in ion-beam induced charge (IBIC) images demonstrates transient charge losses around Te inclusions and dislocations. [11,12] All these defects can significantly degrade the crystal properties and consequently deteriorate the performances of devices. Thus, the comprehensive study of these defects is quite important for the better understanding of the crystal properties and detector performance.…”

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