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 Å, are realized. The structures with relatively small dots (≈80 Å) exhibit properties predicted earlier for quantum dot (QD) lasers such as low threshold current densities (below 100 A cm−2) and ultrahigh characteristic temperatures (T0 = 350 to 425 K). For temperatures of operation above 100 to 130 K T0 decreases and the threshold current density increases (up to 0.95 to 3.3 kA cm−2 at room temperature) due to carrier evaporation from QPs. Larger InAs QPs (≈140 Å) 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 Å) being close to ≈1.8 to 2 ns, respectively. A significant decrease in radiative lifetime is realized in vertically‐coupled quantum dots 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.