The composition effect on the thermal and optical properties across CdZnTe crystals

Abstract

Cd 1-x Zn x Te mixed crystals investigated in this work were grown from the melt by vertical Bridgman-Stockbarger method in the whole range of composition 0<x<1 that is from one binary crystal (CdTe) to another (ZnTe). The real composition of grown crystals was measured with SEM/EDS method along growth axis. The segregation coefficient of Zn in CdTe matrix has been evaluated as close to unity. The energy gap as a function of the composition was determined from transmission spectroscopy. Thanks to that bowing parameter of this ternary alloy was found to be 0.458. In this work for the first time the systematical study of thermal properties of Cd 1-x Zn x Te alloys from one binary crystal (CdTe) to another (ZnTe) grown by vertical Bridgman technique were undertaken. The thermal diffusivity and effusivity of investigated crystals were derived from the experimental data and allowed calculating the thermal conductivity. Diagrams of the thermal conductivity versus composition were analyzed applying model for mixed semiconducting crystals given by Sadao Adachi. Thanks to that contribution of the thermal resistivity arising from the lattice disorder to the total resistivity of the crystal has been determined.

Quantitative Imaging of Defect Distributions in CdZnTe Wafers Using Combined Deep-Level Photothermal Spectroscopy, Photocarrier Radiometry, and Lock-In Carrierography

“…Cd 0.9 Zn 0.1 Te crystals were grown using the high-temperature and high-pressure vertical Bridgman–Stockbarger method . Pure binary powders of CdTe and ZnTe (6N, Koch-Light), mixed together in a stoichiometric proportion, were placed inside a graphite crucible, kept at a temperature of about 1650 K for a few hours, and then the ingot was extracted from the heating zone at a speed of 2.4 mm/h.…”

“…Obtained ingots were sectioned with a wire saw perpendicular to the growth axis into about 1 mm thick slices (wafers), which were not oriented along any specific crystallographic plane. The wafers were polished and inspected with the scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) method, leading to the conclusion that the zinc content along the growth axis did not vary substantially among all crystals and, therefore, the segregation coefficient of zinc in the CdTe matrix was close to unity.…”

“…Rapidly growing applications of CdZnTe as a material suitable for X-ray and γ-ray detector fabrication − and for high-efficiency solar cells , have introduced the urgent need for characterization of photocarrier properties and their associated solid-state transport parameters, including their spatial distributions in wafer substrates, which affect charge transport and limit the performance of optoelectronic devices. Most popular diagnostic methods in use are current deep-level transient spectroscopy (I-DLTS), transient current technique (TCT), current and capacitance vs voltage ( I – V and C – V ) measurements, γ-ray spectroscopy, Hall measurements, and optical and thermal measurements. − Beyond those methodologies, photocarrier radiometry (PCR) is a nondestructive and noncontacting spectrally gated frequency-domain dynamic semiconductor photoluminescence (PL) diagnostic modality, which allows for the simultaneous nondestructive determination of electronic transport parameters in semiconductor substrates and devices. − Subsequently, lock-in carrierography (LIC) was introduced as a near-infrared (NIR) imaging extension of PCR, aimed at constructing quantitative images of carrier transport parameters. − Next, two-beam heterodyne LIC (HeLIC) was introduced to address the need for high-frequency photocarrier excitation, eliciting fast enough signal responses required to measure short recombination lifetimes and other fast photocarrier relaxation processes. HeLIC was developed to allow high-frequency dynamic imaging of optoelectronic material and device properties, which require sampling rates orders of magnitude higher than those achievable by the frame rates of today’s fastest NIR camera technologies. − Very recently, heterodyne PCR (HePCR) proved to be very sensitive to photocarrier emission/capture processes out of, and into, band-gap defect and impurity states: a newly discovered HePCR phenomenon giving rise to a frequency-domain heterodyne signal amplitude depression (“dip” or “notch”) accompanied by a 180° phase transition was attributed to a nonlinear kinetic mechanism of laser-excited harmonic carrier density waves (CDW) interacting with trap or defect states in Si wafers .…”

Study of the Thermal Properties and Lattice Disorder Effects in CdTe–Based Crystals: CdBeTe, CdMnTe, and CdZnTe

“…In recent decades, these crystals have been one of the most usable and studied materials. The variation in composition allows for changing their energy band gap and lattice constant, which is very useful from an application point of view [13]. On the other hand, CdMnTe (CMT) crystals show desirable properties for spintronics applications due to their magneto-optical properties [14].…”

On Investigations of the Optical Absorption Coefficient of Gold and Germanium Implanted Silicon with the Use of the Non-destructive Contactless Photo Thermal Infrared Radiometry

“…12 In this work we report results of investigations of Au 2+ and Ge + ion-implanted silicon with the Photo Thermal Infrared Radiometry (PTR) method. 13 This method is used for investigations of semiconductor materials like other photoacoustic (PA), [14][15][16][17][18][19][20] photopyroelectric [21][22][23] and Modulated Free Carriers Absorption (MFCA) [24][25][26][27][28] methods. The PTR method has a wide range of different applications in investigations of many types of materials.…”