Optical Gain Spectrum and Confinement Factor of a Monolayer Semiconductor in an Ultrahigh-Quality Cavity.

Two-dimensional (2D) semiconductors have attracted great attention as a novel class of gain materials for low-threshold, on-chip coherent light sources. Despite several experimental reports on lasing, the underlying gain mechanism of 2D materials remains elusive due to a lack of key information, including modal gain and the confinement factor. Here, we demonstrate a novel approach to directly determine the absorption coefficient of monolayer WS2 by characterizing the whispering gallery modes in a van der Waals microdisk cavity. By exploiting the cavity's high intrinsic quality factor of 2.5 × 104, the absorption coefficient spectrum and confinement factor are experimentally resolved with unprecedented accuracy. The excitonic gain reduces the WS2 absorption coefficient by 2 × 104 cm-1 at room temperature, and the experimental confinement factor is found to agree with the theoretical prediction. These results are essential for unveiling the gain mechanism in emergent, low-threshold 2D-semiconductor-based laser devices.

Ge0.95Sn0.05 Gate-All-Around p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors with Sub-3 nm Nanowire Width.

We demonstrate Ge0.95Sn0.05 p-channel gate-all-around field-effect transistors (p-GAAFETs) with sub-3 nm nanowire width (WNW) on a GeSn-on-insulator (GeSnOI) substrate using a top-down fabrication process. Thanks to the excellent gate control by employing an aggressively scaled nanowire structure, Ge0.95Sn0.05 p-GAAFETs exhibit a small subthreshold swing (SS) of 66 mV/decade, a decent on-current/off-current (ION/IOFF) ratio of ∼1.2 × 106, and a high-field effective hole mobility (µeff) of ∼115 cm2/(V s). In addition, we also investigate quantum confinement effects in extremely scaled GeSn nanowires, including threshold voltage (VTH) shift and IOFF reduction with continuous scaling of WNW under 10 nm. The phenomena observed from experimental results are substantiated by the calculation of GeSn bandgap and TCAD simulation of electrical characteristics of devices with sub-10 nm WNW. This study suggests Ge-based nanowire p-FETs with extremely scaled dimension hold promise to deliver good performance to enable further scaling for future technology nodes.

Integration of InGaAs MOSFETs and GaAs/ AlGaAs lasers on Si Substrate for advanced opto-electronic integrated circuits (OEICs).

Lasers monolithically integrated with high speed MOSFETs on the silicon (Si) substrate could be a key to realize low cost, low power, and high speed opto-electronic integrated circuits (OEICs). In this paper, we report the monolithic integration of InGaAs channel transistors with electrically pumped GaAs/AlGaAs lasers on the Si substrate for future advanced OEICs. The laser and transistor layers were grown on the Si substrate by molecular beam epitaxy (MBE) using direct epitaxial growth. InGaAs n-FETs with an ION/IOFF ratio of more than 106 with very low off-state leakage and a low subthreshold swing with a minimum of 82 mV/decade were realized. Electrically pumped GaAs/AlGaAs quantum well (QW) lasers with a lasing wavelength of 795 nm at room temperature were demonstrated. The overall fabrication process has a low thermal budget of no more than 400 °C.

Monolithic integration of InGaAs n-FETs and lasers on Ge substrate.

We report the first monolithic integration of InGaAs channel field-effect transistors with InGaAs/GaAs multiple quantum wells (MQWs) lasers on a common platform, achieving a milestone in the path of enabling low power and high speed opto-electronic integrated circuits (OEICs). The III-V layers used for realizing transistors and lasers were grown epitaxially on the Ge substrate using molecular beam epitaxy (MBE). A Si-CMOS compatible process was developed to realize InGaAs n-FETs with subthreshold swing SS of 93 mV/decade, ION/IOFF ratio of more than 4 orders of magnitude with very low off-state leakage current, and a peak effective mobility of more than 2000 cm2/V·s. In addition, fabrication process uses a low overall processing temperature (≤ 400 °C) to maintain the high quality of the InGaAs/GaAs MQWs for the laser. Room temperature electrically-pumped lasers with a lasing wavelength of 1.03 µm and a linewidth of less than 1.7 nm were realized.

Non Infiltrating Angiolipoma of the Palate in Geriatric Patient: A Case Report with Review of Literature.

Angiolipoma is one of the rare variant of lipoma. This benign tumour consists of both fatty and vascular elements. It mostly occur in the trunk and extremities and is uncommon in head and neck region. Angiolipoma is classified as infiltrating and non- infiltrating types. Among all neoplasms of the oral cavity, lipomas account for 1 to 5% and the incidence of angiolipoma is 5 to 17% in it. There is no sex predilection for this tumour. It is classified as infiltrative and non-infiltrative type. Surgical excision is the method to be considered for both the types of angiolipoma, however the infiltrating type recurs post-surgery. We report a rare case report of 55-year-old female with non-infiltrating angiolipoma of the hard palate mimicking a mucocele treated by surgical excision with no signs of recurrence and good wound healing after three months follow up with minimal scar formation.