InAs-GaAs quantum dots: From growth to lasers

Injection lasers based on InAs-GaAs and InGaAs-GaAs quantum pyramids (QPs) with a lateral size ranging from 80 to 140 A are realized. The structures with relatively small dots (80 A) exhibit properties predicted earlier for quantum dot (QD) lasers such as low threshold current densities (below 100 A cm -2 ) and ultrahigh characteristic temperatures (To = 350 to 425 K). For temperatures of operation above 100 to 130 K T 0 decreases and the threshold current density increases (up to 0.95 to 3.3 kA cm -2 at room temperature) due to carrier evaporation front QPs. Larger InAs QPs (140 A) providing better carrier localization exhibit saturation of the ground state emission and enhanced nonradiative recombination rate at high excitation densities. The radiative lifetime shows a weak dependence on the dot size (80 to 140 A) being close to 1.8 to 2 ns. respectively. A significant decrease in radiative lifetime is realized in vertically-coupled quantum clots formed by a QP shape-transformation effect. The final arrangement represents a three-dimensional tetragonal array of InAs islands inserted in a GaAs matrix each composed of several vertically merging InAs parts. The first injection lasing in such an array is achieved.