Self-organized growth of strained InGaAs quantum disks

LATERAL confinement of electrons or excitons in low-dimensional semiconductor structures (quantum ‘wires’ and ‘boxes’) leads to new electronic properties1, which can be used to improve the performance of optical devices such as semiconductor lasers and nonlinear optical switches2–4. Several state-of-the-art technologies have been applied to fabricate these quantum structures: lateral structure can be defined using high-resolution lithography combined with dry etching5,6, or by crystal growth on masked substrates7,8. Unfortunately, such processes inevitably result in a deterioration of the crystal quality. But recent reports9,10 of self-organized formation of quantum-wire semiconductor structures have attracted considerable interest as a means of overcoming these difficulties. We describe here the self-organized formation of box-like microstructures during the interrupted epitaxial growth of strained InGaAs/AlGaAs multilayer structures on (311)B gallium arsenide substrates. We find that the InGaAs layers organize spontaneously into homogeneous nanoscale disks embedded in an AlGaAs matrix. This phenomenon appears to arise from a complex interplay between the lattice strain, surface energy and surface migration.