GeSn Lasers Covering a Wide Wavelength Range Thanks to Uniaxial Tensile Strain

Abstract

Silicon photonics continues to progress tremendously, both in near-infrared datacom/telecoms and in mid-IR optical sensing, despite the fact a monolithically integrated group IV semiconductor laser is still missing. GeSn alloys are one of the most promising candidate materials to realize such devices, as robust lasing under optical pumping was demonstrated by several groups up to mild cryogenic temperatures. Ideally, the integrated lasers should be tunable by design over a wide spectral range, offering a versatility that is required for optical sensing devices. We present here an innovative approach, taking advantage of local strain management in the semiconductor laser’s active zone. Arrays of differently strained Fabry-Pérot GeSn microlasers were fabricated side-by-side on the very same chip after blanket epitaxy on a Ge-buffered silicon-on-insulator substrate. Thanks to the local strain design, laser emission over a very large wavelength range under optical pumping, with laser lines peaking from 3.1 up to 4.6 μm at 25 K and with thresholds lower than 10 kW·cm–2. Laser operation persists up to 273 K, that is, very close to room temperature. This strategy, implemented on group IV semiconductors, opens up a new route to control the emission properties of microlasers integrated on a chip over significant photon energy windows representing a significant step forward in the integration and miniaturization of light sources emitting at a process-defined wavelength.

All‐Group IV Transferable Membrane Mid‐Infrared Photodetectors

“…Indeed, 3D complex membrane structures can be realized by selectively releasing to engineer lattice parameter and bandgap energy and directness. GeSn direct bandgap is achieved at a Sn content around 10 at% in fully relaxed layers, leading to the recent demonstration of room temperature optical emission up to ≈4 µm [34][35][36] and optically pumped lasers at 3.1-3.4 µm operating at temperatures of 180-270 K. [37][38][39] PDs were also demonstrated using GeSn layers showing a room temperature performance close to that of commercial PbSe detectors at wavelengths reaching 3 µm, [40][41][42][43] although the residual strain limits the operation wavelength range. Indeed, GeSn semiconductors are inherently metastable and typically exhibit a compositional gradient and a large compressive strain resulting from the canonical, lattice-mismatched growth on Ge.…”

Carrier lifetime of GeSn measured by spectrally resolved picosecond photoluminescence spectroscopy

“…Germanium-tin alloys are promising materials for electro-optical devices compliant with the existing silicon processing technology [1,2]. It is by now well understood how the composition x and strain of Ge 1−x Sn x films affect the band structure and optical transitions [3,4], and suitable growth techniques have been developed [5,6] for growing direct-bandgap materials of a sufficient quality to obtain laser action [7][8][9][10]. Even though some knowledge exists on structural point [11] and extended [12] defects, their impact on the charge carriers remains unresolved with researchers often resorting to qualified guessing for the carrier lifetimes [13,14].…”

Electro-Absorption Modulation in GeSn Alloys for Wide-Spectrum Mid-Infrared Applications

“…Although significant progress has been made on MIR Si-based waveguides 10 , light emitters [11][12][13][14][15][16] , and photodetectors [17][18][19][20] , efficient MIR optical modulators on Si remain elusive because group-IV semiconductors do not exhibit the linear electro-optical (Pockels) effect 21 .…”