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Gregory Salamo

Publications and source records attributed to Gregory Salamo.

8 recordsLinked to original sources
arXiv2026

Investigation of GeSn aspect ratio trapping growth up to 8% Sn

Aspect ratio trapping (ART) growth of germanium-tin (GeSn) is a promising approach to target important objectives on the quest towards commercialization of complementary metal-oxide-semiconductor (CMOS)-compatible GeSn optoelectronics devices. Its local growth on patterned substrate allows for versatile device integration into photonics integrated circuit or for stand-alone structure like focal plane array imager. Additionally, high aspect ratio from nano-sized window can terminate early threading dislocation propagation on the oxide sidewalls, leaving subsequent growth defect-free and potentially improving the device performance. Knowledge remains missing regarding GeSn ART growth kinetics, morphology and how they evolve from thin film growth, with successful growth itself yet to be demonstrated. In this work, we report GeSn ART growth up to 8% Sn. Two configurations -- self-induced Ge core/GeSn shell for Sn content between 6% and 8%, and bulk GeSn ART for Sn content below 1% -- are observed. We present a comprehensive study on GeSn ART growth kinetics through different growth rounds and designs, showing a link between pyramid shape of ART island and successful Sn incorporation, as well as the role of growth selectivity and local heating.

cond-mat.mtrl-sci↗
arXiv2026

Study of GeSn Selective Area Growth with Demonstration of SWIR Light Detection

As germanium-tin (GeSn) epitaxial growth quality continuously improves, the search for an efficient integration strategy of GeSn optoelectronics devices into complementary metal-oxide-semiconductor (CMOS) manufacturing line also accelerates. Selective area growth (SAG) on patterned substrate emerges as a promising approach for this quest, with locally controlled growth of GeSn laser/detector suitable for either co-integration with silicon-based waveguide structure or stand-alone module like focal plane array. In this work, we report successful GeSn SAG with Sn content ranging from 3.2% to 8.7% of good optical quality, with demonstration of tunable GeSn SAG photoluminescence and GeSn SAG photoconductor device, the latter with detection cutoff wavelength up to 2 um. In addition, we present a comprehensive study of GeSn SAG condition at different window sizes, from 2 um to 100 um, and shapes: circle, square, octagon, and rectangle. Presence of loading effect is revealed, where GeSn growth rate increases as pattern fill factor and window size shrink. It introduces a different growth condition compared to thin film growth, which can weaken or inhibit Sn incorporation at very small window size and induce Sn segregation in high Sn content SAG growth.

physics.app-ph↗
arXiv2026

Interface-Driven Growth Mode Control of 2D GaSe on 3D GaAs Substrates with Distinct Crystallographic Orientations

Previous studies of the growth of two-dimensional (2D) gallium selenide (GaSe) by molecular beam epitaxy (MBE) on a gallium arsenide (GaAs) three-dimensional (3D) substrate have reported significant differences in growth morphology, polytype, and the nature of the interface. The results differ, ranging from GaSe 2D film growth at tilted 2D planes to observed spiral structures, thereby calling for a deeper understanding of the impact of the substrate interface on the growth of GaSe films. In this paper, we conduct a comprehensive reexamination of the growth mechanism of GaSe on GaAs substrates with (211)B and (001)B orientations, investigating the nature of the 2D/3D interface and the resulting morphology of the 2D GaSe films. We do this by investigating different methods of preparation of the GaAs substrate surface before the growth of GaSe by MBE, the importance of which has not been considered before. Our results resolve the mechanistic origin of tilted versus non-tilted 2D growth and establish a general interface-driven orientation selection rule linking substrate symmetry and dangling-bond coordination to layered heteroepitaxy. This framework provides a scalable interface-engineering pathway for deterministic control of layered chalcogenide heterostructures and enables wafer-scale integration with established semiconductor device platforms.

cond-mat.mtrl-sci↗
arXiv2025

Study of electronic band alignment in SiGeSn/GeSn quantum well via internal photoemission effect

SiGeSn-based optoelectronic devices, which operate across a broad infrared wavelength range, have attracted significant attention, particularly heterostructures utilizing quantum wells are widely utilized. In these structures, band alignment type and barrier height are crucial for carrier confinement, making them highly desirable information to obtain. This work leverages the internal photoemission effect to extract effective barrier heights from a Si0.024Ge0.892Sn0.084 / Ge0.882Sn0.118 single quantum well structure, which was pseudomorphically grown on Ge0.9Sn0.1 and Ge buffered Si substrate. The extracted effective barrier heights are approximately 22{plus minus}2 and 50{plus minus}2 meV for electrons and holes, respectively. Moreover, we have identified the type-I band alignment between GeSn well and SiGeSn barrier, as indicated by an internal photoemission threshold of 555 {plus minus} 1 meV.

physics.app-ph↗
arXiv2020

Electrically injected GeSn lasers with peak wavelength up to 2.7 micrometer at 90 K

GeSn lasers enable monolithic integration of lasers on the Si platform using all-group-IV direct-bandgap materials. Although optically pumped GeSn lasers have made significant progress, the study of the electrically injected lasers has just begun only recently. In this work, we present explorative investigations of electrically injected GeSn heterostructure lasers with various layer thicknesses and material compositions. The cap layer total thickness was varied between 240 and 100 nm. At 10 K, a 240-nm-SiGeSn capped device had a threshold current density Jth = 0.6 kA/cm2 compared to Jth = 1.4 kA/cm2 of a device with 100-nm-SiGeSn cap due to an improved modal overlap with the GeSn gain region. Both devices had a maximum operating temperature Tmax = 100 K. Device with cap layers of Si0.03Ge0.89Sn0.08 and Ge0.95Sn0.05, respectively, were also compared. Due to less effective carrier (electron) confinement, the device with a 240-nm-GeSn cap had a higher threshold Jth = 2.4 kA/cm2 and lower maximum operating temperature Tmax = 90 K, compared to those of the 240-nm-SiGeSn capped device with Jth = 0.6 kA/cm2 and Tmax = 100 K. In the study of the active region material, the device with Ge0.85Sn0.15 active region had a 2.3 times higher Jth and 10 K lower Tmax, compared to the device with Ge0.89Sn0.11 in its active region. This is likely due to higher defect density in Ge0.85Sn0.15 rather than an intrinsic issue. The longest lasing wavelength was measured as 2682 nm at 90 K. The investigations provide guidance to the future structure design of GeSn laser diodes to further improve the performance.

physics.app-ph↗
arXiv2020

Electrically injected GeSn lasers on Si operating up to 100 K

The significant progress of GeSn material development has enabled a feasible solution to the long-desired monolithically integrated lasers on the Si platform. While there are many reports focused on optically pumped lasers, GeSn lasers through electrical injection have not been experimentally achieved yet. In this work, we report the first demonstration of electrically injected GeSn lasers on Si. A GeSn/SiGeSn heterostructure diode grown on a Si substrate was fabricated into ridge waveguide laser devices and tested under pulsed conditions. Special considerations were given for the structure design to ensure effective carrier confinement and optical confinement that lead to lasing. Lasing was observed at temperatures from 10 to 100 K with emission peaks at around 2300 nm. The minimum threshold of 598 A/cm2 was recorded at 10 K and the threshold increased to 842 A/cm2 at 77 K. The spectral linewidth of a single peak was measured as small as 0.13 nm (0.06 meV). The maximum characteristic temperature was extracted as 99 K over the temperature range of 10-77 K.

physics.app-ph↗
arXiv2013

Advanced holographic nondestructive testing system for residual stress analysis

The design and operating of a portable holographic interferometer for residual stress analysis by creating a small scratch along with a new mathematical algorithm of calculations are discussed. Preliminary data of the stress investigations on aluminum and steel alloys have been obtained by the automatic processing of the interference pattern using a notebook computer. A phase-shift compensation technique in real-time reflection interferometry is used to measure the out-of-plane stress release surface displacement surrounding a small scratch (25 um depth and 0.5 mm width) in a plate with residual stress of around 50 MPa. Comparison between theoretical models for a rectangular and triangular shaped scratch with the experimental data are presented.

physics.optics↗