HgZnTe Research Articles

The miscibility gap in cadmium, mercury and zinc telluride systems: Theoretical description

Miscibility gap locations in the CdTe–ZnTe and HgTe–ZnTe systems are calculated yielding the critical parameters ( T c / K , x c (second compound)) (407, 0.38) and (558, 0.33), respectively. The obtained functions allow us to predict the location of the miscibility gap in the CdTe–HgTe–ZnTe system based on the Kohler and Redlich–Kister–Muggianu procedures. Ternary phase diagrams for the Hg–Cd–Te, Cd–Zn–Te and Hg–Zn–Te systems in the subsolidus region are also estimated based on known thermodynamic properties of the binary systems and our results for the quasi-binary alloys in the paper.

Scanning tunneling optical spectroscopy in mercury cadmium telluride and related compounds

We consider II–VI narrow gap semiconducting alloys: mercury cadmium telluride, Hg (1− x) Cd ( x) Te (MCT), mercury zinc telluride, Hg (1− x) Zn ( x) Te (MZT), and mercury zinc selenide, Hg (1− x) Zn ( x) Se (MZS). MCT is emphasized for actual calculations, but a table of values needed in all calculations is presented. These materials are of interest because of their application to infrared detectors and related devices, and because they are candidates for low gravity crystal growth to improve uniformity. We present new calculations of the scanning tunneling optical spectroscopy (STOS) current from which the local energy gap, a function of x, and hence the stoichiometry ( x) can be determined as a function of position with presumably high spatial resolution. The low temperature tunneling current (vs. photon frequency) has a sharper onset at the band gap than the low temperature optical absorption. This sharp onset originates from the rapid increase in the integrated transmission probabilities and is greatly enhanced by large diffusion lengths. Thus, STOS should be a competitive technique, compared to optical absorption, for determining the local stoichiometry, a property that is important for characterizing crystals.

Phase diagram of HgTe–ZnTe pseudobinary and density, heat capacity, and enthalpy of mixing of Hg1−xZnxTe pseudobinary melts

In this article, the solidus temperatures of the Hg1−xZnxTe pseudobinary phase diagram for several compositions in the low x region were measured by differential thermal analysis and the HgTe–ZnTe pseudobinary phase diagram was constructed. The densities of two HgZnTe melts, x=0.10 and 0.16, were determined by an in situ pycnometric technique in a transparent furnace over, respectively, 110 and 50 °C ranges of temperature. The thermodynamic properties of the melts, such as the heat capacity and enthalpy of mixing, were calculated for temperatures between the liquidus and 1500 °C by assuming an associated solution model for the liquid phase.

Viscosity of Hg0.84Zn0.16Te pseudobinary melt

An oscillating-cup viscometer was developed to measure viscosity of molten HgZnTe ternary semiconductor alloys. Data were collected for the pseudobinary Hg0.84Zn0.16Te melt between 770 and 850 °C. The kinematic viscosity was found to vary from approximately 1.1 to 1.4×10−3 cm2 s−1. A slow relaxation phenomena was also observed for temperatures from the melting point of 770 to ∼800 °C. Possible mechanisms for this effect are discussed.

Phase diagrams and microscopic structures of (Hg,Cd)Te, (Hg,Zn)Te, and (Cd,Zn)Te alloys

A cluster theory based on the quasi-chemical approximation has been applied to study the local correlation bond-length distribution, and phase diagrams of the II-VI pseudobinary alloys Hg(1 - x)Cd(x)Te, Hg(1 - x)Zn(x)Te, and Cd(1 - x)Zn(x)Te. The cluster energy is calculated by letting it relax in some effective alloy medium and then considering the contributions from the strain and chemical energies. Two different models are presented to simulate the alloy medium. While both models show that all three alloys have nearly random distributions, the signs of the local correlation prove to be sensitive to the alloy medium chosen for the energy calculation. Good agreement is found between experiment and the bond lengths and phase diagrams in both models.

Epitaxial growth, characterization, and phase diagram of HgZnTe

Epitaxial layers of Hg1−xZnxTe (0.11≤x≤0.22) were grown by the horizontal liquid-phase epitaxy technique on Cd1−yZnyTe substrates with 0≤y≤0.20. The structural and electrical properties of the Hg1−xZnxTe layers were characterized and compared with those of epitaxial Hg1−xCdxTe. It was found that the structural and electrical properties of long-wavelength infrared (LWIR) HgZnTe, when grown on closely lattice-matched CdZnTe substrates, are comparable to those of high-quality epitaxial LWIR HgCdTe. However, the annealing behavior of the Hg1−xZnxTe layers shows a decreased Hg diffusion rate relative to that in Hg1−xCdxTe. Liquidus temperatures of Te-rich ternary (Hg1−zZnz)1−yTey solutions were measured. The preliminary liquidus data indicate that, in the Te corner, the Hg–Zn–Te and Hg–Cd–Te phase diagrams are very similar.