Systematic study of Si-based GeSn photodiodes with 26 µm detector cutoff for short-wave infrared detection

Abstract

Normal-incidence GeSn photodiode detectors with Sn compositions of 7 and 10% have been demonstrated. Such detectors were based on Ge/GeSn/Ge double heterostructures grown directly on a Si substrate via a chemical vapor deposition system. A temperature-dependence study of these detectors was conducted using both electrical and optical characterizations from 300 to 77 K. Spectral response up to 2.6 µm was achieved for a 10% Sn device at room temperature. The peak responsivity and specific detectivity (D*) were measured to be 0.3 A/W and 4 × 10 cmHzW at 1.55 µm, respectively. The spectral D* of a 7% Sn device at 77 K was only one order-of-magnitude lower than that of an extended-InGaAs photodiode operating in the same wavelength range, indicating the promising future of GeSn-based photodetectors.

Defect-free high Sn-content GeSn on insulator grown by rapid melting growth

“…GeSn is an attractive semiconductor for Si-based photonics due to its special energy band structure and the compatibility with complementary metal oxide semiconductor (CMOS) processes12345678. GeSn with tunable direct bandgap from 0.8 eV to 0 eV has great potential in developing Si-based infrared photodetectors.…”

“…GeSn with tunable direct bandgap from 0.8 eV to 0 eV has great potential in developing Si-based infrared photodetectors. Si-based GeSn photodetectors have been achieved working at near-infrared56 and short-wave infrared wavelength range78, which are mostly dominated by direct-bandgap group III-V materials. Meanwhile, GeSn also is the most promising material for achieving efficient Si-based group IV light source.…”

“…However, due to the large lattice constant, high Sn-content GeSn layer grown on Si substrate usually has the poor material quality and under unexpected compressive strain. Compressive strain increases the energy difference between Γ valley and L valley in conduction band of GeSn, and offsets the bandgap shrink induced by Sn incorporation, which prevents direct bandgap transformation and high absorption coefficient45789. For these reasons, the key to enhance the optical absorption and light emission performance is not only promoting the Sn-content and crystal quality, but also relaxing the compressive strain (even obtains tensile strain) of GeSn layer.…”

“…Despite these difficulties, significant efforts have been made in growing GeSn by chemical vapor deposition (CVD)4710 and molecular beam epitaxy (MBE)1111213 under non-equilibrium condition at low temperature, which is used to suppress segregation of Sn. In order to increase Sn-content in GeSn layer, grown temperature has to reduce further, which could be achieved using MBE.…”

Design of a high-speed germanium-tin absorption modulator at mid-infrared wavelengths

“…The recent demonstration of a direct bandgap Germanium-Tin (GeSn) IRB laser [2], [3] offers the prospect of establishing a complete group IV mid-IR platform, provided reliable electrically pumped room temperature lasing can be reached. Important progress has already been made on extended wavelength GeSn photodetectors [4], [5]. On the other hand, only a few studies have been made on the realization of GeSn modulators.…”