Photo detection and modulation from 1,550 to 2,000 nm realized by a GeSn/Ge multiple-quantum-well photodiode on a 300-mm Si substrate

Abstract

A GeSn/Ge multiple-quantum-well (MQW) p-i-n photodiode structure was proposed for simultaneously realizing high detectivity photo detection with low dark current and effective optical modulation based on the quantum confined Stark (QCSE) effect. The MQW stacks were grown on a 300-mm Ge-buffered Si substrate using reduced pressure chemical vapor deposition (RPCVD). GeSn/Ge MQW p-i-n photodiodes with varying mesa diameters were fabricated and characterized. An ultralow dark current density of 16.3 mA/cm2 at -1 V was achieved as expected due to the low threading dislocation density (TDD) in pseudomorphic GeSn layer. Owing to the ultralow dark current density and high responsivity of 0.307 A/W, a high specific detectivity of 1.37×1010 cm·Hz1/2/W was accomplished at 1,550 nm, which is comparable with commercial Ge and extended-InGaAs photodetectors. Meanwhile, the bias voltage-dependent photo response was investigated from 1,700 to 2,200 nm. The extracted effective absorption coefficient of GeSn/Ge MQW shows a QCSE behavior with electric field-dependent exciton peaks from 0.688 to 0.690 eV. An absorption ratio of 1.81 under -2 V was achieved at 2 μm, which shows early promise for effective optical modulation. The high frequency response was calculated theoretically, and the predicted 3-dB bandwidth for the photodiode with a mesa diameter of 30 μm could reach 12 GHz at -2 V.

Review of Si-Based GeSn CVD Growth and Optoelectronic Applications

“…Nevertheless, the peak specific detectivity for the GeSn detector was compared to other commercial infrared detectors at a wavelength range from 1400 to 3000 nm, which showed that peak specific detectivity of the GeSn detector at 2000 nm was only one order of magnitude lower than that of the extended-InGaAs detector ( Figure 22 ). To improve device performance, Xu S, et al attempted to create a GeSn/Ge MQW detector [ 67 , 68 ], a GeSnOI detector [ 69 ], and a photon-trapping microstructure GeSn/Ge MQW detector [ 209 ].…”

“…The wavelength cutoff was extended to be at least 1750 nm, which means that the GeSn photodetector with a 2% Sn content can cover the entire telecommunication band. Since then, GeSn photoconductor detectors [ 58 , 59 , 60 , 61 , 62 , 63 ], and p–GeSn/i–GeSn/n–GeSn heterostructure detectors [ 64 , 65 , 66 , 67 , 68 ] have been demonstrated. Advances in GeSn CVD growth technology have occurred alongside material quality and detector performance improvements, including: (i) the wavelength cutoff for the GeSn photodetector has been progressively broadened from 1800 nm to 2100, 2400, 2600, 2650, and 3650 nm [ 63 ]; (ii) based on wafer-bonding technology, the dark current for GeSn photodetector has been suppressed by more than two orders of magnitude [ 69 ]; (iii) peak specific detectivity values are now comparable to those of commercial extended-InGaAs detectors (4 × 10 10 cm·Hz 1/2 ·W −1 ) at the same wavelength range; (iv) a passivation technique was developed to enhance responsivity and peak specific detectivity [ 65 ]; and (v) mid-IR imaging was demonstrated with GeSn photodetectors, and the image quality of the GeSn photodetectors was found to be superior to that of a commercial PbSe detector [ 63 ].…”

Near-Infrared Photoresponse in Ge/Si Quantum Dots Enhanced by Photon-Trapping Hole Arrays

“…The high on/off ratio of the devices around – is observed, manifesting good rectifying behavior. For the device with a flat surface, the dark current is 0.13 mA/cm 2 at a reverse bias of 1 V. This value is two orders of magnitude lower than previously reported ones for Ge-on-Si [ 30 , 43 , 44 ] and GeSn/Ge [ 45 ] photodiodes with dislocation-rich Ge active layers. The ultralow dark current density in Ge/Si QDIPs is attributed to the formation of dislocation-free Ge QDs by strain-driven self-organization through the Stranski–Krastanov growth mode.…”

GeSn Waveguide Photodetectors with Vertical p–i–n Heterostructure for Integrated Photonics in the 2 μm Wavelength Band

“…In addition, obtaining a high operational device speed requires a low series resistance due to the reduced resistance capacitance (RC) delay. [ 37 ] The dark current density ( J dark ) at −1 V was 27.23 A cm −2 , which is relatively high compared to the typical value of 0.1–30 A cm −2 of normal‐incidence GeSn PDs with similar Sn contents. [ 25,37 ] The relatively high dark current density is attributed to the long device length that leads to higher peripheral leakage current.…”