ORDERED ARRAYS OF QUANTUM DOTS - FORMATION, ELECTRONIC-SPECTRA, RELAXATION PHENOMENA, LASING

Elastic relaxation on facet edges, renormalization of the surface ener gy of the facets, and interaction between islands via the strained sub strate are the driving forces for self-organization of ordered arrays of uniform coherent three-dimensional islands on crystal surfaces. For a (100) surface of a cubic crystal, two-dimensional square lattice of pyramid-like islands (quantum dots) with the periodicity along the di rections of the lowest stiffness [010] and [001] has the minimum energ y among different one-dimensional and two-dimensional arrays. For the InAs/GaAs(100) system, an equilibrium array of dots of the lateral siz e similar to 120-140 Angstrom exists in a fixed range of growth parame ters. The main luminescence peak at 1.1 eV, as well as peaks of excite d states coincide bl energy with the peaks revealed in the calorimetri c absorption spectra regardless of the amount of InAs deposited (2-5 M L). Raman spectra indicate significant strain in InAs dots. The ''phon on bottleneck'' effect is bypassed via multi-phonon exciton and carrie r relaxation. Ultranarrow lines(< 0.15 meV) are observed in cathodolum inescence spectra up to high temperatures. Low threshold current densi ty operation via zero-dimensional states and ultrahigh temperature sta bility of the threshold current (T-0 = 450 K) are realized for a quant um dot injection laser. Increase in the gain and significant reduction in the radiative lifetime are possible via the self-organization of v ertically-coupled quantum dots (VECODs) arranged in a well ordered art ificial three-dimensional tetragonal lattice.