Bandgap tuning in ZnxCd1-xTe superlattices through variable atomic ordering.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Superlattices offer tunable electronic and optical properties.
• ZnxCd1-xTe alloys are promising semiconductor materials.
• Understanding structure-property relationships in superlattices is key for material design.

Purpose of the Study:

• To explore the full structural configuration space of 32-layer ZnxCd1-xTe superlattices.
• To identify structures that minimize and maximize the bandgap across all zinc concentrations.
• To investigate the influence of stacking order on physical properties.

Main Methods:

• Utilized valence force field dynamics, empirical pseudopotential method, and folded spectrum method for structural searching.
• Employed density functional theory with hybrid functionals for property calculations.
• Developed an alternate preconditioner to enhance the efficiency of the locally optimal preconditioned conjugate gradient method.

Main Results:

• Discovered that the bandgap of ZnxCd1-xTe superlattices can vary by up to 0.2 eV due to stacking order.
• Formation energies, bandgaps, densities of states, effective masses, and optical response functions were calculated.
• Calculated properties show good agreement with available experimental data.
• Stacking order significantly affects effective masses irregularly, while optical properties remain largely insensitive.

Conclusions:

• Stacking sequence is a critical parameter for controlling the bandgap in ZnxCd1-xTe superlattices.
• The findings provide a pathway for precise bandgap engineering in these materials.
• This work advances the understanding of nanoscale material design for optoelectronic applications.