Atomic structure and optical properties of InAs submonolayer depositions in GaAs

Abstract

Using cross-sectional scanning tunneling microscopy and photoluminescence spectroscopy, the atomic structure and optical properties of submonolayer depositions of InAs in GaAs are studied. The submonolayer depositions are formed by a cycled deposition of 0.5 monolayers InAs with GaAs spacer layers of different thicknesses between 1.5 and 32 monolayers. The microscopy images exhibit InAs-rich agglomerations with widths around 5 nm and heights of up to 8 monolayers. A lateral agglomeration density in the 1012cm -2 range is found. During the capping of the InAs depositions a vertical segregation occurs, for which a segregation coefficient of 0.73 was determined. In the case of thin GaAs spacer layers, the observed segregation forms vertically connected agglomerations. The photoluminescence spectra exhibit peaks with linewidths below 10 meV and show a considerable dependence of the peak energy on the spacer thickness, even up to 32 monolayers GaAs, indicating a long range e lectronic coupling

Heterodimensional charge-carrier confinement in stacked submonolayer InAs in GaAs

“…The undoped SML structures are surrounded by a 300-nm-thick GaAs matrix which is then sandwiched by Al x Ga 1−x As barriers to prevent escape of photogenerated carriers. Further details of the growth procedure may be found elsewhere [15,16]. As a reference, an undoped 6.5-nm-thick In 0.18 Ga 0.82 As QW on GaAs was grown at 600…”

Cross-sectional scanning tunneling microscopy of InAs/GaAs(001) submonolayer quantum dots

“…It has been reported that due to segregation of indium along the growth direction, indium from the bottom layers segregates and coalesces with indium from the top layers and forms In-rich clusters or agglomerates that behave like quantum dots [14]. The desired height and composition are achieved by optimizing the number of deposition cycles as well as by optimizing the GaAs-spacer thickness [6]. The zero-dimensional behavior of SMLQDs has been reported in many works [15][16][17].…”

“…The submonolayer (SML) technique is considered as an alternative to the SK growth mode to obtain a higher dot density, smaller aspect ratio, to get a better control of their size and composition, and to avoid the formation of the wetting layer [6,7]. The main idea behind the growth of submonolayer QDs (SMLQDs) is to deposit a fraction of a monolayer (ML) of a low-band-gap material forming monolayer-thick islands which are then covered by a few MLs of a high-band-gap material and the cycle is repeated.…”

Mode-locking Instabilities for High-Gain Semiconductor Disk Lasers Based on Active Submonolayer Quantum Dots

“…In this paper, we want to explore the potential of submonolayer (SML) QDs [28] as active media for high-peak-power ultrafast SDLs. The growth of SML superlattices involves a cycled deposition of InAs submonolayers capped with a few monolayers of GaAs, creating a vertically correlated InAs agglomeration with typically high areal densities of the order of 10 12 cm −2 [29]. The heterodimensional morphology of SML QDs combines the beneficial signatures of a zero-dimensional (0D) confinement such as high excitonic gain and very fast gain dynamics with the large DOS and high modal gain usually featured by 2D-confined structures [30].…”