SWIR and MWIR photodetector technologies are mainly served by III-V and II-VI materials such as InSb, InGaAs, and HgCdTe which are costly, require cooling, and face manufacturing and scalability challenges. GeSn is an attractive group IV material that is Si-compatible with the potential to circumvent these challenges by enabling the fabrication of SWIR and MWIR detectors on a scalable and cost-effective Si platform. In this work, material development and optoelectrical properties of a set of heterostructures made of Si/Ge/GeSn are presented. The material properties and its potential application in photodetectors are discussed. For instance, at a low Sn content (below 5 at.%), we found that GeSn-based photoconductive devices display unexpectedly a low dark current and exhibit a room-temperature cutoff wavelength of 1.75 um and a responsivity of 0.52 A/W at 1.55 um. Results from microscopic and spectroscopic studies are also presented. Finally, capacitance devices are fabricated to extract unintentional doping concentrations from CV measurements.
This conference presentation, “A method based on complementary transmission and reflection measurements for extracting the optical properties of a thin film” was presented at the Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XV conference at SPIE Photonics West 2022.
In the quest for practical group IV lasers, researchers have proposed a few ideas such as strain engineering of Ge and alloying of Sn into Ge. Both approaches fundamentally alter bandstructure such that Ge can become a direct bandgap material. Recently, relaxation of limiting compressive strain and addition of mechanical tensile strain have been employed to improve the lasing performance. However, such strain engineering has thus far been possible only in suspended device configurations, which significantly limit heat dissipation and hinder the device performance. We herein demonstrate GeSn microdisk lasers fully released on Si that relax the limiting compressive strain and achieve excellent thermal conduction.
GeSn alloys have emerged as a promising material for realizing CMOS-compatible light sources. GeSn lasers demonstrated to date have large device footprints and active areas, which limit the realization of densely integrated lasers operating at low power consumption. Thanks to their intrinsically small device form factors, 1D photonic crystal lasers may offer opportunities to overcome such limitations of large GeSn lasers. Here, we present a 1D photonic crystal nanobeam laser with a very small device footprint (~7 μm2) and a compact active area (~1.2 μm2) on a GeSn-on-insulator substrate.
Combining Sn alloying and tensile strain to Ge has emerged as the most promising engineering approach to create an efficient Si-compatible lasing medium. The residual compressive strain in GeSn has thus far made the simple geometrical strain amplification technique unsuitable for achieving tensile strained GeSn. Herein, by utilizing two unique techniques, we report the introduction of a uniaxial tensile strain directly into GeSn micro/nanostructures. By converting GeSn from indirect to direct bandgap material via tensile strain, we achieve a 10-fold increase in the light emission intensity.
KEYWORDS: Short wave infrared radiation, Nanowires, Silicon, Heterojunctions, Silicon photonics, Tin, Chemical species, Transmission electron microscopy, Compound semiconductors, Control systems
Sn-containing group IV semiconductors (Si)GeSn represent a versatile platform to implement a variety of Si-compatible photonic, optoelectronic, and photovoltaic devices. This class of semiconductors provides two degrees of freedom, strain and composition, to tailor the band structure and lattice parameter thus laying the groundwork to implement novel heterostructures and low-dimensional systems on a Si substrate. In this presentation, we will discuss the recent progress in controlling and understanding the opto-electronic properties of metastable (Si)GeSn semiconductor nanowires and heterostructures. We will shed new light on the basic mechanisms governing their epitaxial growth and thermal stability. We will also discuss the opto-electronic properties and present strategies to integrate these material systems in the fabrication of short wavelength infrared (SWIR) and mid-infrared (MIR) detectors and light emitting devices.
Commercially available light-emitting diodes (LEDs) suffer from low-efficiency in the green region of the visible
spectrum. In order to solve this issue III-V materials such as Gallium phosphide (GaP) can be investigated. GaP in the
zinc blende (ZB) crystal structure has an indirect band gap, limiting the efficiency of the green emission. However, when
the material is grown with wurtzite (WZ) crystal phase a direct band gap is predicted. Here, we show the fabrication and
the characterization of wurtzite GaP nanowires, together with the demonstration of the direct band gap. The strong
photoluminescence signal observed at 594 nm with a lifetime in the order of 1ns matches with the expectation for a
direct band gap material. Furthermore, the emission wavelength can be tuned across a wide range of the visible spectrum
(555−690 nm) by incorporating aluminum or arsenic in the WZ GaP nanowires.
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