The strong correlation between advancing the performance of Si microelectronics and their demand of low power consumption requires new ways of data communication. Photonic circuits on Si are already highly developed except for an eligible on-chip laser source integrated monolithically. The recent demonstration of an optically pumped waveguide laser made from the Si-congruent GeSn alloy, monolithical laser integration has taken a big step forward on the way to an all-inclusive nanophotonic platform in CMOS. We present group IV microdisk lasers with significant improvements in lasing temperature and lasing threshold compared to the previously reported nonundercut Fabry−Perot type lasers. Lasing is observed up to 130 K with optical excitation density threshold of 220 kW/cm 2 at 50 K. Additionally the influence of strain relaxation on the band structure of undercut resonators is discussed and allows the proof of laser emission for a just direct Ge 0.915 Sn 0.085 alloy where Γ and L valleys have the same energies. Moreover, the observed cavity modes are identified and modeled.

We present results on CVD growth and electro-optical characterization of Ge(0.92)Sn(0.08)/Ge p-i-n heterostructure diodes. The suitability of Ge as barriers for direct bandgap GeSn active layers in different LED geometries, such as double heterostructures and multi quantum wells is discussed based on electroluminescence data. Theoretical calculations by effective mass and 6 band k∙p method reveal low barrier heights for this specific structure. Best configurations offer only a maximum barrier height for electrons of about 40 meV at the Γ point at room temperature (e.g. 300 K), evidently insufficient for proper light emitting devices. An alternative solution using SiGeSn as barrier material is introduced, which provides appropriate band alignment for both electrons and holes resulting in efficient confinement in direct bandgap GeSn wells. Finally, epitaxial growth of such a complete SiGeSn/GeSn/SiGeSn double heterostructure including doping is shown.

Guided by the Wentzel-Kramers-Brillouin approximation for band-to-band tunneling (BTBT), various performance boosters for Si TFETs are presented and experimentally verified. Along this line, improvements achieved by the implementation of uniaxial strain in nanowires (NW), the benefits of highk/metal gates, and newly engineered tunneling junctions as well as the effect of scaling the NW to diameters of 10 nm are demonstrated. Specifically, self-aligned ion implantation into the source/drain silicide and dopant segregation has been exploited to achieve steep tunneling junctions with less defects. The obtained devices deliver high on-currents, e.g., gate-all-around (GAA) NW p-TFETs with 10 nm diameter show I D = 64 μA/μm at V DS = V GS − V off = −1.0 V, and good inverse subthreshold slopes (SS). Tri-gate TFETs reach minimum SS of 30 mV/dec. Dopant segregation helps to minimize the defect density in the junction and thus trap assisted tunneling (TAT) is reduced. Pulsed current-voltage (I-V) measurements have been used to investigate TAT. We could show that scaled NW devices with multigates are less vulnerable to TAT compared to planar devices due to a shorter tunneling path enabled by the inherently good electrostatics. Furthermore, SiGe NW homo-and heterojunction TFETs have been investigated. The advantages of a SiGe/Si heterostructure as compared to a homojunction device are revealed and the effect of line tunneling which results in an increased BTBT generation is demonstrated. It is also shown that complementary strained Si TFET inverters and p-TFET NAND gates can be operated at V DD as low as 0.2 V. This suggests a great potential of TFETs for ultralow power applications. The analysis of GAA NW TFETs for analog applications provided a high transconductance efficiency and large intrinsic gain, even higher than for state-of-the-art 20 nm FinFETs at low voltages.

ABSTRACT(Si)GeSn is an emerging, group IV alloy system, offering new exciting properties, with great potential for low power electronics due to the fundamental direct bandgap and prospects as high mobility material. In this article we present a systematic study of HfO2/TaN high-k/metal gate stacks on (Si)GeSn ternary alloys and low temperature processes for large scale integration of Sn

Certain GeSn alloys are group IV direct bandgap semiconductors with prospects for electrical and optoelectronical applications. In this letter, we report on the temperature dependence of the electrical characteristics of high Sn-content Ge0.89Sn0.11 p-i-n diodes. NiGeSn contacts were used to minimize the access resistance and ensure compatibility with silicon technology. The major emphasis is placed on the negative differential resistance in which peak to valley current ratios up to 2.3 were obtained. TCAD simulations were performed to identify the origin of the various current contributions, providing evidence for direct band to band tunneling and trap assisted tunneling.