Temperature dependent spectral response and detectivity of GeSn photoconductors on silicon for short wave infrared detection

Abstract

The GeSn direct gap material system, with Si complementary-metal-oxide semiconductor (CMOS) compatibility, presents a promising solution for direct incorporation of focal plane arrays with short wave infrared detection on Si. A temperature dependence study of GeSn photoconductors with 0.9, 3.2, and 7.0% Sn was conducted using both electrical and optical characterizations from 300 to 77 K. The GeSn layers were grown on Si substrates using a commercially available chemical vapor deposition reactor in a Si CMOS compatible process. Carrier activation energies due to ionization and trap states are extracted from the temperature dependent dark I-V characteristics. The temperature dependent spectral response of each photoconductor was measured, and a maximum long wavelength response to 2.1 μm was observed for the 7.0% Sn sample. The DC responsivity measured at 1.55 μm showed around two orders of magnitude improvement at reduced temperatures for all samples compared to room temperature measurements. The noise current and temperature dependent specific detectivity (D*) were also measured for each sample at 1.55 μm, and a maximum D* value of 1 × 10(9) cm·√Hz/W was observed at 77 K.

Optical Characterization of Si-Based Ge1−x Sn x Alloys with Sn Compositions up to 12%

“…1 Among the various material systems that could be integrated on Si, the Ge 1Àx Sn x alloy has attracted much attention recently due to the following reasons: (1) Capability of monolithic integration on Si; 2 (2) Availability of direct bandgap material; 3 and (3) tunable bandgap covering broad shortwave-and mid-infrared (IR) wavelength range. 4 During the last decade, the GeSn-based optically pumped laser, 5 light emitting diode, [6][7][8][9][10][11][12] photo detector [13][14][15][16][17][18][19][20] have been demonstrated, and the GeSn modulator has been investigated 21,22 which make up a complete set of components for Si photonics. For these prototype devices, the material characteristics have turned out to be the decisive factor for the performance of the device.…”

High-speed detection at two micrometres with monolithic silicon photodiodes

“…Silicon photonic components are fabricated using complementary metal-oxide semiconductor (CMOS)-compatible technologies, with the potential for integration with electronic control. Recently, groups have demonstrated several silicon-based components operating in the MIR wavelength range of 2-20 μm, including low-loss waveguides, couplers, splitters and multiplexers 11 , as well as some with hybrid active functionality 12,13 . However, photodetectors that are compatible with silicon waveguides, are capable of detection beyond 2 μm, and operate at the bandwidths required by future optical communication networks remain elusive.…”

“…At this early stage in development, the GeSn devices reported thus far have relatively high leakage current with no high-speed functionality demonstrated near 2 µm (ref. 13). An interesting alternative approach, with potential for integration with silicon, comprises the use of graphene-based photodetectors 14 , but the waveguide-integrated devices demonstrated to date have not demonstrated efficient responsivity and high bandwidth simultaneously.…”

Si based GeSn photoconductors with a 1.63 A/W peak responsivity and a 2.4 μm long-wavelength cutoff

“…Active photonic Ge 1-x Sn x devices such as light emitting diodes, 5-8 photoconductors, [9][10][11] and photodiodes 12,13 demonstrate that high quality growth can be achieved from both CVD 14 and MBE systems. 9,10 Photoconductors are advantageous for early detector technology development due to the low background doping concentrations and reduced fabrication complexity.…”