Zinc-Stabilized Manganese Telluride with Wurtzite Crystal Structure

Abstract

Alloying of semiconductors with similar crystal structures is often used to fine-tune materials properties for optoelectronic applications. However, examples of semiconductor alloys between compounds with two different crystal structures, where properties are changing dramatically as a function of composition, are much rarer. Even more unusual are such heterostructural alloys where the structure and properties can be changed with only a small amount of substitution (<10%). One exception is yttria-stabilized zirconia (YSZ) with cubic fluorite crystal structure, used for a wide range of applications. Here, we report on experimental observation of such unusual behavior in zincstabilized manganese telluride (ZSMT), and on theoretical explanation of its compositional stabilization in the wurtzite crystal structure. Thin films of Mn 1−x Zn x Te alloys synthesized at 400 °C change from the nickeline (NC) to the wurtzite (WZ) crystal structure at x as low as 0.08. Theoretical calculations indicate that this structural transition occurs due to small MnTe polymorph energy differences, and strong preference of Zn atoms to adopt tetrahedral vs octahedral coordination environment. The calculated 1 eV increase of the band gap from NC to WZ structure is consistent with the experimental measurements on ZSMT films. These measurements also indicate 1000−10 000 times lower conductivity than the nickeline MnTe, due to low ZSMT hole concentration. Overall, the wide band gap and low hole density make ZSMT a promising candidate for p-type transparent transistors and other optoelectronic applications.

Wide Band Gap Chalcogenide Semiconductors

“…Additionally, many computationally "metastable" structures can be stabilized, for example by heterostructural alloying techniques. 37 Thus, ahead of us lies exciting and challenging research to uncover new wide band gap chalcogenide materials with potential use in energy applications and beyond. Chalcogenides and mixed chalcogenides are further categorized by anion type, with "mixed" referring to any mixed chalcogenide.…”

Accessing Metastability in Heterostructural Semiconductor Alloys

“…Since the structural transitions depend strongly on the polymorph ordering in the endmember compounds, it is possible to control the transition points by choosing suitable alloying materials combinations. This has recently been demonstrated in Mn 1‐ x Zn x Te alloys where the structural transition from the NA to the WZ structure is observed at even lower alloying concentrations than in MnSe 1‐ x Te x , mainly due to different polymorph formation energies in ZnTe . By tuning the structural transitions points, high‐energy polymorphs of the endmembers can be stabilized at relatively small alloying concentrations.…”

“…different polymorph formation energies in ZnTe. [56,57] By tuning the structural transitions points, high-energy polymorphs of the endmembers can be stabilized at relatively small alloying concentrations. This is particularly interesting when these polymorphs are impossible to access with other stabilization methods.…”

Wurtzite materials in alloys of rock salt compounds

“…Similarly, in the selenides, the RS structure of MnSe was converted to the WZ structure in the Zn 1Àx Mn x Se alloys [7]. In the tellurides, by alloying NC MnTe with trace amount of ZB ZnTe, the ground state switched from the narrow band gap NC structure to the wide band gap WZ structure [8,9]. Despite the success of alloying for stabilization of WZ MnO, MnSe, and MnTe, there is only one report on using alloying to stabilize WZ MnS [4].…”