Negative bi-exciton binding energy in (211)B InAs/GaAs piezoelectric quantum dots G.E. Dialynas 1 , C. Xenogianni 1,2 , E. Trichas 1.2 , P.G. Savvidis 1,2 , G. Constantinidis 1 , Z. Hatzopoulos 1,3 , N.T. Pelekanos 1,2 1 Microelectronics Research Group, IESL/FORTH, P.O. Box 1527, 71110 Heraklion, Greece 2 Department of Materials Science and Technology, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece 3 Physics Department, University of Crete, P.O. Box 2208, 71003 Heraklion, Crete, Greece Abstract: We report on isolated dot spectroscopy of polar (211)InAs/GaAs quantum dots grown by MBE. Exciton and biexciton peaks have been identified, revealing a negative biexciton binding energy attributed to the presence of strong piezoelectric field. © 2007 Optical Society of America OCIS codes: (250.5230) Photoluminescence; (260.6580) Stark effect Arsenide quantum dots (QDs) have been intensively studied in recent years due to their potential for unique optoelectronic applications and quantum optics demonstrations, based on their discrete atomic-like density of states [1]. In spite of the intense experimental effort, however, photoluminescence (PL) studies on QD samples are typically plagued by large inhomogeneous PL linewidths. Thus, single dot spectroscopy is the appropriate method in order to study their optical and electronic properties. The majority of the investigated QD heterostructures has been grown on (100) GaAs. However, in recent years, increasing attention has been devoted to the study of high index GaAs substrates, especially on (N11) GaAs. Strained heterostructure growth on polar (N11) substrates induces electrical polarization between the group III and group V ions, generating a piezoelectric field along the growth axis [2]. This field, which can readily exceed 100kV/cm, depending on N and on the magnitude of strain, is expected to modify drastically the opto-electronic properties. In this paper, we present an investigation of isolated InAs QDs grown on polar (211)GaAs and we emphasize on the piezoelectric field effects on the optical properties of InAs QDs. For this work, InAs QDs have been grown on GaAs(211) by molecular beam epitaxy (MBE). Growth details are reported elsewhere [3]. The role of several growth parameters as temperature and growth rate has been investigated, and the QD samples have been characterized by atomic force microscopy (AFM) and PL. AFM measurements indicate an extremely low QD density of 1.610 9 cm -2 , with an average height of 5nm and an aspect ratio of 10, as illustrated in Fig. 1.The linewidth of the PL spectrum is 55meV, which is attributed to electron-hole recombination in the InAs QDs. Fig.1 AFM image of (211) InAs/GaAs grown by MBE at T=500˚C. Notice the low QD density of the sample Fig. 2. SEM photo of the sample’s surface after the Cr/Al mask deposition. Both latex beads and circular apertures of 300 nm diameter can be observed. Isolated dot spectroscopy was performed using a cw He-Cd laser, emitting at 325nm as the excitation source. In order to probe isolated QDs, an Al/Cr shadow mask with circular apertures of a few hundreds of nm has been fabricated on the surface, as depicted in Fig.2. The processing of the sample’s surface included the deposition of 300nm diameter polystyrene latex beads (spin coating), evaporation of 95nm Al/5nm Cr mask and a lift-off a1422_1.pdf JTuA6.pdf