Comparison of InAs quantum dots grown on GaInAsP and InP

Abstract We report on the growth of InAs quantum dots (QDs) on GaInAsP and InP buffers by metal-organic chemical vapour deposition on InP(100) substrates. Indium segregation and the As-P exchange reaction affect the QD nucleation and composition. The As-P exchange reaction has a more pronounced effect on the QDs grown on the InP buffer than on those grown on the GaInAsP buffer. A very thin (0.6 nm) GaAs interlayer grown between the buffer layer and the InAs QD layer consumes segregated indium and minimizes the As/P exchange reaction. Wavelength tuning from 1450 to 1750 nm covering the technologically important 1550 nm wavelength is also achieved for the InAs QDs grown with the thin GaAs interlayer. (Some figures in this article are in colour only in the electronic version) Self-assembled InAs quantum dots (QDs) on InP are very promising for long wavelength optoelectronic device applications (1.3-2 µm). Their potential use in optical fibre communications (1.3-1.55 µm) and atmospheric pollution control systems has attracted more efforts [1-5] to grow InAs QDs on the relatively small lattice mismatch substrate InP (3.2%). However the main difficulty associated with this material system is the As/P exchange reaction which occurs above 360 • C The InAs QDs are grown on (100) semi-insulating (SI) InP substrates using a horizontal flow MOCVD reactor at the pressure of 180 mbar. Trimethylindium (TMI), trimethylgallium (TMG), PH 3 and AsH 3 are used as precursors, and H 2 as a carrier gas. The InAs QDs are grown on InP or lattice matched Ga 0.25 In 0.75 As 0.54 P 0.46 buffer layers at 520 • C using a V/III ratio of 15. The growth temperature for the rest of the structure is 650 • C. Following an oxide desorption step for the substrate at 700 • C for 10 min under PH 3 , a 200 nm InP buffer layer is grown. Then InAs QDs are deposited directly on the InP buffer layer or on a 50 nm lattice matched GaInAsP (λ g = 1.28 µm) buffer grown on top of the InP layer. In some samples, a 0.6 nm thick GaAs interlayer is grown at 65