heterojunktów

Heterojunctions (heterojunktów in Polish) are interfaces that form between two dissimilar semiconductor materials, typically with different band gaps, electron affinities, or lattice constants. The most common example occurs in devices such as heterojunction bipolar transistors, light‑emitting diodes, and quantum‑well lasers, where the distinct electronic properties of each constituent material allow for efficient carrier separation, confinement, and enhanced performance. At the junction, a built‑in potential is established due to the difference in Fermi levels, creating a depletion region that controls the flow of electrons and holes. The band alignment can be of the type I (straddling gap), type II (staggered gap), or type III (broken gap) revealing distinct carrier dynamics in each case. Material combinations frequently used include GaAs/AlGaAs, InP/InGaAs, and Si/SiGe, each chosen to balance lattice matching, strain management, and band‑gap engineering. Device fabrication requires precise molecular‑beam epitaxy or metal‑organic chemical vapor deposition to preserve interface sharpness and reduce defects. Advances in heterojunction design have enabled high‑efficiency solar cells, high‑electron mobility transistors, and infrared detectors, making them a cornerstone of modern semiconductor technology.