Lasing from excited states in self-assembled InP/GaInP quantum islands

Aiming at laser emission in the visible part of the spectrum, we have inves tigated the growth of self-assembled InP quantum dots on GaInP by low-press ure metal-organic vapour phase epitaxy using the Stranski-Krastanow growth mode. These InP islands show a photoluminescence emission energy of 1.72 eV (90 K) at low excitation densities. Lasing was observed on optically pumpe d laser structures with a single layer of InP dots, GaInP waveguide materia l and AlInP cladding layers above an excitation density of 1.3 kW cm(-2) at 90 K. The detected laser line is located at 1.8 eV, about 80 meV higher th an the ground-state transition energy. We attribute this behaviour to lasin g from excited states in agreement with power-dependent photoluminescence e xperiments and photoluminescence excitation measurements, and gain measurem ents using the variable stripe length method. These laser structures show s timulated emission under optical pumping up to room temperature above excit ation densities of 30 kW cm(-2). Furthermore, injection lasers with Si- and Zn-doped (Al0.5Ga0.5)InP cladding layers have been realised where lasing o ccurred above a threshold current density of 290 A cm(-2) with an emission line at 1.78-1.82 eV (90 K). (C) 2000 Elsevier Science S.A. All rights rese rved.