Suppression of dark current in germanium-tin on silicon p-i-n photodiode by a silicon surface passivation technique

Abstract

We demonstrate that a complementary metal-oxide-semiconductor (CMOS) compatible silicon (Si) surface passivation technique effectively suppress the dark current originating from the mesa sidewall of the Ge(0.95)Sn(0.05) on Si (Ge(0.95)Sn(0.05)/Si) p-i-n photodiode. Current-voltage (I-V) characteristics show that the sidewall surface passivation technique could reduce the surface leakage current density (Jsurf) of the photodiode by ~100 times. A low dark current density (Jdark) of 0.073 A/cm(2) at a bias voltage of -1 V is achieved, which is among the lowest reported values for Ge(1-x)Sn(x)/Si p-i-n photodiodes. Temperature-dependent I-V measurement is performed for the Si-passivated and non-passivated photodiodes, from which the activation energies of dark current are extracted to be 0.304 eV and 0.142 eV, respectively. In addition, the optical responsivity of the Ge(0.95)Sn(0.05)/Si p-i-n photodiodes to light signals with wavelengths ranging from 1510 nm to 1877 nm is reported.

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

“…The shunt resistance is mainly coming from the following facts: 1) There is surface recombination due to the lack of surface passivation. This part of the shunt resistance can be eliminated by applying passivation technique reported in [20]; 2) Since a wet chemical etching process was used for the mesa etch, some Sn could be re-deposited on the mesa surface and sidewall, resulting in the shunt current.…”

“…The relatively high surface leakage current density is mainly due to two causes: 1) no surface passivation technique was applied on the sidewalls of photodiode device; and 2) the narrowed bandgap of the Ge 1-x Sn x alloy leads to more thermally excited carriers. The dark current can be reduced by a passivation technique either using Si [20] or yttrium-doped GeO 2 [29] as the passivation layer.…”

“…In order to improve the device performance in terms of spectral response and specific detectivity (D*), the GeSn photodiode with high Sn composition and low dark current is preferred. Some preliminary results on GeSn photodiodes have been reported recently [10][11][12][13][14][15][16][17][18][19][20]. In this work, a systematic study of the Ge/Ge 1-x Sn x /Ge double heterostructure (DHS) photodiode with Sn compositions of 7 and 10% has been conducted.…”

“…Developing high-performance GeSn detectors is strongly motivated by these facts: 1) the market-dominating detectors operating in the SWIR wavelength range rely mainly upon III-V (such as InGaAs and InSb and HgCdTe) techniques [1,2], that are incompatible with Si complementary metal-oxide-semiconductor (CMOS) processes, resulting in limited sizes of focal plane arrays (FPAs) and high cost; 2) the GeSn technique offers a viable low-cost solution at these wavelengths for large-scale FPAs monolithically integrated on Si; 3) owing to the tremendous effort made to develop material growth including chemical vapor deposition (CVD) and molecular beam epitaxy (MBE), device-level material quality of GeSn has been achieved; 4) our previous study showed 2.4 µm photo-response cutoff with a responsivity of 2.85 A/W at 1.55 µm and 77 K from a 10% Sn photoconductor, which exceeded the Ge (0.8 A/W) and InGaAs (1.0 A/W) photovoltaic detectors operating at the same wavelength [2,3]; 5) an uncooled GeSn detector FPA (256 × 256 upon a readout integrated circuit) has been achieved recently [4]. For the past five years, multiple Ge 1-x Sn x detectors have been designed and fabricated and their characteristics have been investigated [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In order to improve the device performance in terms of spectral response and specific detectivity (D*), the GeSn photodiode with high Sn composition and low dark current is preferred.…”

Study of GeSn Mid-infrared Photodetectors for High Frequency Applications

“…Over the last 10 years, many GeSn-based photodetectors have been reported with their performance dramatically improved. The responsivity of photodetectors keeps increasing as well as more Sn incorporation in the materials, which extends cut-off wavelength to mid-infrared ranges (Mathews et al, 2009;Su et al, 2011;Werner et al, 2011;Kim et al, 2013;Tseng et al, 2013;Zhang et al, 2013;Peng et al, 2014;Dong et al, 2015;Chang et al, 2016;Pham et al, 2016;Huang et al, 2017;Tran et al, 2018). However, only a few reports are available discussing the high-speed capability of the GeSn photodetectors (Oehme et al, 2014;Dong et al, 2017;Xu et al, 2019).…”