Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 20: Poster I

HL 20.5: Poster

Dienstag, 18. März 2025, 10:00–12:30, P3

Characterization of surfaces of mixed semiconductor crystals — •Marsel Karmo¹ and Martin Brehm² — ¹Warburger Str. 100 33098 Paderborn — ²Warburger Str. 100, 33098 Paderborn

Compositionally disordered crystals, also known as mixed-crystals, play a crucial role in semiconductor engineering. They enable the manipulation of material properties such as the band gap, which is important for opto-electronic devices like solar cells. Additionally, these crystals are used as buffer layers to mitigate strain from lattice constant mismatches between different material layers. However, accurately describing mixed crystals theoretically presents significant challenges. Due to the random occupation of atomic sites it is not possible to introduce a unit cell in other words the crystal as a whole is the unit cell. This prohibits also the use of boundary conditions. A commonly used approach to approximate mixed crystals is the Supercell Method (SCM), which employs a large, unit cell with random atomic site occupations. While this method approximates a mixed crystal, it is limited by computational resources. Another approach is the Virtual Crystal Approximation (VCA), which replaces the mixed crystal with an analytically averaged system. This method reduces the computational effort by using a smaller unit cell but may overlook local atomic environments, potentially limiting its ability to capture certain physical properties. In this work, we compare these two methods, VCA and SCM within the Vienna Ab Initio Simulation Package (VASP) to evaluate their performance in calculating the electronic structure and surface formation energy.

Keywords: Virtual Crystal Approximation