GaAs1xGex

GaAs1−xGex is a semiconductor alloy in which a fraction x of arsenic atoms in gallium arsenide (GaAs) is replaced by germanium. The material largely preserves the zinc blende crystal structure at low to moderate Ge content, and its lattice constant can be tuned with composition. By Vegard’s law, the lattice parameter follows a_GaAs1−xGex ≈ (1−x)a_GaAs + x a_Ge, allowing gradual variation of strain when grown on different substrates.

Growth and structure are typically achieved through epitaxial techniques such as molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). These methods enable precise control of the Ge content and the creation of graded or patterned layers for devices such as quantum wells or buffer layers.

Electronic properties of GaAs1−xGex are composition-dependent. The band gap energy can be engineered by varying x, generally decreasing as Ge content increases. The conduction-band minimum in GaAs is at the Γ point, while in Ge it lies at the L point, so increasing Ge content alters the band structure and can lead to a direct-to-indirect transition under certain conditions or strains. Temperature and strain also influence the band structure and carrier dynamics.

Applications and research focus include band-gap engineering for optoelectronic and high-speed electronic devices, infrared and near-infrared detectors, and approaches to lattice-matched integration with silicon technology. GaAs1−xGex thus offers a platform for tunable electronic and optical properties within the GaAs material system.