multiquantumwell

Multiquantumwell refers to a semiconductor heterostructure that stacks many thin quantum wells separated by barrier layers. Each well is a potential well for charge carriers, and the series of wells creates a superlattice in which electron and hole wavefunctions extend over multiple periods. By controlling the thickness and composition of the wells and barriers, as well as the number of periods, designers can tailor the band structure, optical transition energies, and density of states. This enables wavelength-tunable absorption and emission and enhanced optical gain.

Common material systems include GaAs/AlGaAs, InGaAsP/InP, and GaN/AlGaN, each offering different wavelength ranges from near-infrared to blue/UV. Well thicknesses are typically a few nanometers, with barrier layers slightly thicker; the exact values determine the confinement energy and the strength of coupling between adjacent wells. Effects such as the quantum-confined Stark effect and intersubband transitions are exploited in devices when appropriate.

Applications of multiquantumwells span light-emitting diodes, laser diodes, and photodetectors. In laser diodes, MQWs provide high differential gain and lower threshold currents. In LEDs, multiple wells can improve radiative efficiency and color control. In photodetectors and modulators, MQWs enable tailored absorption spectra and fast response.

Fabrication generally relies on epitaxial growth methods such as molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD). Achieving uniform well/barrier thicknesses and minimizing strain-induced defects are key challenges, particularly in lattice-mismatched systems. Ongoing research seeks to optimize interdiffusion control and compositional precision to expand material choices and device performance.