The use of a high-growth-temperature GaAs spacer layer is demonstrated to significantly improve the performance of 1.3μm multilayer self-assembled InAs∕InGaAs dot-in-a-well lasers. The high-growth-temperature spacer layer inhibits threading dislocation formation, resulting in enhanced electrical and optical characteristics. Incorporation of these spacer layers allows the fabrication of multilayer quantum-dot devices emitting above 1.3μm, with extremely low room-temperature threshold current densities and with operation up to 105°C.

The structural and optical properties of GaAs1−xBix alloys for x up to 0.108 have been investigated by high resolution X‐ray diffraction and photoluminescence (PL). At room temperature (RT), the PL intensity of the GaAs0.97Bi0.03 sample was found to be ∼300 times higher than a GaAs control sample grown at the same temperature (400 °C). PL measurements carried out at 10 K show that when excitation power, Pex was increased from 0.11 to 1140 W cm−2, the PL peak energy blue‐shifts by 80 meV while the full‐width‐at‐half‐maximum reduces from 115 to 63 meV. However, the PL peak emission energy becomes independent of the excitation power at RT. The results indicate the presence of localized energy states in the GaAs0.97Bi0.03 sample, which trap carriers at low temperatures and that the majority of the carriers become delocalized at RT. Furthermore, the temperature dependent PL also shows an S‐shape behavior, which is a signature of localization effects. A theoretical model, which was derived by solving a rate equation was employed. The model successfully reproduces the observed S‐shape behavior and the theory fits well with the experimental data. The RT band gap of GaAs1−xBix for x up to 0.108 has been plotted and compared with the literature.

Abstract-This paper describes the design, fabrication, and performance of planar-geometry InGaAs-InP devices which were specifically developed for single-photon detection at a wavelength of 1550 nm. General performance issues such as dark count rate, single-photon detection efficiency, afterpulsing, and jitter are described.

It is demonstrated that the emission of InAs quantum dots ͑QDs͒ capped with GaAsSb can be extended from 1.28 to 1.6 m by increasing the Sb composition of the capping layer from 14% to 26%. Photoluminescence excitation spectroscopy is applied to investigate the nature of this large redshift. The dominant mechanism is shown to be the formation of a type-II transition between an electron state in the InAs QDs and a hole state in the GaAsSb capping layer. The prospects for using these structures to fabricate 1.55 m injection lasers are discussed. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2173188͔ Self-assembled InAs/ GaAs quantum dots ͑QDs͒ are of considerable interest due to their physical properties and potential applications, for example, long wavelength GaAsbased QD lasers operating in the 1.3-1.6 m telecommunications wavelength range. 1 High-performance InAs/ GaAs QD lasers, with emission close to 1.3 m, have been demonstrated using InGaAs, InAl͑Ga͒As, and GaAsSb capping layers ͑CLs͒ to directly cover the InAs QDs. [2][3][4][5][6] In addition, there have been a number of attempts to extend the emission wavelength beyond 1.5 m, with room-temperature ͑RT͒ photoluminescence ͑PL͒ above 1.5 m having been demonstrated for large InAs/ GaAs QDs, 7 GaInNAs/ GaAs QDs, 8 InAs QDs with an In 0.45 Ga 0.55 As CL, 9 InAs QDs with InGaNAs CL, 10 and InAs QDs grown on InGaAs or GaAsSb metamorphic buffer layers. 11,12 In a previous letter, we reported ϳ1.3 m emission from InAs QDs with a GaAsSb CL. 6 Evidence for a type-II system for Sb compositions Ͼ14% was obtained, and a 1.3 m laser was fabricated. In the present letter we show that RT emission at 1.6 m may be obtained by increasing the Sb composition to 26%. The compositional dependence of the electronic band structure is probed using a combination of PL and PL excitation ͑PLE͒.The samples were grown in a V80H molecular beam epitaxy system equipped with conventional solid sources for group-III elements and EPI cracker sources for As and Sb. The QDs were formed by depositing 2.8 monolayers ͑MLs͒ of InAs at a rate of ϳ0