Advanced GeSn/SiGeSn Group IV Heterostructure Lasers

Abstract

Growth and characterization of advanced group IV semiconductor materials with CMOS‐compatible applications are demonstrated, both in photonics. The investigated GeSn/SiGeSn heterostructures combine direct bandgap GeSn active layers with indirect gap ternary SiGeSn claddings, a design proven its worth already decades ago in the III–V material system. Different types of double heterostructures and multi‐quantum wells (MQWs) are epitaxially grown with varying well thicknesses and barriers. The retaining high material quality of those complex structures is probed by advanced characterization methods, such as atom probe tomography and dark‐field electron holography to extract composition parameters and strain, used further for band structure calculations. Special emphasis is put on the impact of carrier confinement and quantization effects, evaluated by photoluminescence and validated by theoretical calculations. As shown, particularly MQW heterostructures promise the highest potential for efficient next generation complementary metal‐oxide‐semiconductor (CMOS)‐compatible group IV lasers.

Experimental Calibration of Sn‐Related Varshni Parameters for High Sn Content GeSn Layers

“…[] were extracted from the Raman measurements, but with a Raman–strain relation from ref. [] being different from ours in Equation . After applying our own strain–Raman relation as per Equation , we found a good match between spectra peak wavelengths and our computed bandgap energies matched the spectral peaks in ref.…”

“…Our model fits the data provided in ref. [] where Ge 0.855 Sn 0.145 (DHS1) and Ge 0.86 Sn 0.14 (DHS2) were explored. The PL spectra show a maximum of emission at 20 K at 0.475 and 0.486 eV for DHS1 and DHS2, respectively.…”

Investigation of carrier confinement in direct bandgap GeSn/SiGeSn 2D and 0D heterostructures

“…The crystal orientation in this work is taken to be (001), i.e. QWs are assumed to be grown on the (001) substrate surface, as it is typical in epitaxy 16 . The band structure calculation methods used in this work have been described elsewhere 19 , 20 , 22 .…”

“…Both the experiments and theoretical band alignment calculations indicate that Ge is unsuitable as a barrier material to confine carriers in direct bandgap GeSn wells 14 . On the other hand, a significant improvement in optical performance was demonstrated in GeSn/SiGeSn heterostructures 15 , 16 . Publications on GeSn/SiGeSn bulk heterostructures and quantum wells (QWs) agree on the suitability of SiGeSn as a barrier material for QWs, but an overview and investigation of the influence of doping and absorption processes on material gain is still missing 17 , 18 .…”

Study of Si-Based GeSn Optically Pumped Lasers With Micro-Disk and Ridge Waveguide Structures

“…True direct bandgap GeSn was experimentally identified in 2014 [15], and this was followed by the first demonstration of an optically pumped GeSn band-to-band laser using a Fabry-Pérot (F-P) cavity in early 2015 [16]. Since then, GeSn lasing has been reported by various research groups worldwide [17][18][19][20][21][22][23][24][25][26]. To improve laser performance, various approaches have been applied to facilitate population inversion and carrier and optical confinement, such as using a heterostructure (HS), a multi-quantum-well (MQW) layer structure, or a micro-disk optical cavity.…”