Molecular epitaxy of pseudomorphic Ge_1−ySn_y(y= 0.06–0.17) structures and devices on Si/Ge at ultra-low temperatures via reactions of Ge₄H₁₀and SnD₄

Abstract

A low-pressure CVD technique was specifically developed to prepare a new class of pseudomorphic Ge 1−y Sn y layers, with an Sn content up to 17% on Ge-buffered Si(100) wafers. The growth is conducted via reactions of SnD 4 and the recently deployed Ge 4 H 10 custom precursor, whose large molecular weight and enhanced reactivity enables depositions at unprecedented ultra-low temperatures (150 °C-200 °C), and at pressures akin to those typically employed in solid/gas-source MBE. The thicknesses of the layers far exceed the critical limits predicted by thermodynamic considerations and are either comparable to, or larger than, those observed for MBE-grown samples. This is validated by modeling of the thickness versus the composition for the fully strained and partially relaxed alloys produced in this work relative to the MBE and CVD-grown analogs reported in the literature. Furthermore, the practical relevance of the technique was demonstrated by creating highly doped n-type alloys, which were then used as active layers to fabricate degenerate pn junctions. It was also found that the strained films gradually relax with increasing thickness, providing new types of strain-free material with enhanced optical quality relative to those produced by standard CVD methods, as evidenced by the photoluminescence studies. The strain relaxation mechanism appears to be similar to that observed in CVD-grown samples, with no sign of epitaxial breakdown or precipitous degradation of the bulk crystallinity or surface morphology, in spite of the low growth temperatures employed. Finally, we note that this method represents the first example of a chemically driven route that delivers materials with the desirable properties afforded by MBE, while offering the potential for those practical applications inherent to large-scale CVD.

Emerging technologies in Si active photonics

“…For laser applications, it is paramount to achieve both high Sn composition and strong PL emission at the same time. The development of SnD 4 precursor played in important role in GeSn CVD growth in the early days [70] . A remarkable feature of this precursor is that the GeSn film can directly relax on the Si substrate at a deposition temperature of 200-350 °C without the need of a Ge/Si virtual substrate.…”

A comparative study of selective dry and wet etching of germanium–tin (Ge1−xSnx) on germanium

“…Thanks to the progress in molecular beam epitaxy (MBE) [14,15] and chemical vapor deposition [16][17][18] technologies, Ge 1−x Sn x with x up to 0.34 can be realized. However, due to the large lattice mismatch between α-Sn (6.489 Å) and Ge (5.646 Å) or Si (5.431 Å) of about 15% and 20% [19], respectively, a GeSn epilayer on Ge or Si alloyed with a high Sn content has a large compressive strain, which hinders the bandgap conversion.…”

Si-Based GeSn Photodetectors toward Mid-Infrared Imaging Applications

“…Research activities in GeSn-based detectors have experienced a strong increase in the past a few years. Developing high-performance GeSn detectors has been enabled by the following progresses: i) broad operation wavelength coverage up to 12 µm by increasing the Sn compositions; [5][6][7][8] ii) true direct bandgap allowing for enhanced band-to-band light absorption; [5][6] iii) a complete Si complementary metal-oxide-semiconductor (CMOS) compatible process for material growth; iv) a viable low-cost solution for large-scale focal plane arrays (FPAs) monolithically integrated on Si; v) a readily available growth technique using industry standard reactors to reach device-level material quality; 1,4,[7][8][9][10][11] and vi) a GeSn-based 320×256 FPA imaging sensor with spectra response in the 1.6-1.9 μm range was successfully demonstrated in 2016. 12 In the last a few years, many GeSn-based photodetectors including photoconductors and photodiodes have been reported with dramatically improved performance.…”

“…Research activities in GeSn-based detectors have experienced a strong increase in the past few years. Developing high-performance GeSn detectors has been enabled by the following progresses: (i) broad operation wavelength coverage from 1.55 to 12 μm by varying the Sn compositions; − (ii) true direct bandgap allowing for enhanced band-to-band light absorption; , (iii) a full compatibility with Si complementary metal-oxide-semiconductor (CMOS) for material growth and process; (iv) a viable low-cost solution for large-scale focal plane arrays (FPAs) monolithically integrated on Si; (v) a readily available material growth technique via industrial standard systems with achievable device-level material quality; ,,− and (vi) a GeSn 320 × 256 pixel FPA imaging sensor with 1.6–1.9 μm wavelength spectral response successfully demonstrated in 2016 …”