Effect of bubbles at the bonded interface on the performance of GeSn/Si PIN photodetector

Abstract

Due to the large lattice mismatch between GeSn and Si materials, high-density threading dislocation (TD) forms when GeSn films are grown by epitaxial growth. This leads to the increase of the dark current density (DCD) of the device. The wafer-bonded technique is a promising method to prepare high-quality thin films. This has been used to produce the Si-based GeSn materials with low threading dislocation density (TDD). However, there are a lot of bubbles at the bonded interface, resulting in the deterioration of the performance of the device. The study of bubbles on the performance of the GeSn PIN photodetector (PD) has not been reported. In this paper, the effect of the bonding bubbles on the performance of the device is performed. The photocurrent, dark current, charge concentration, electric field, and 3dB-bandwidth (BW) as a function of the bubble radius and thickness are demonstrated. In addition, the effect of the bubble radius on the 3dB-BW (~18 GHz) is insignificant when the bubble thickness is 1 nm. Similarly, when the bubble radius is 1 μm, the 3dB-BW (~18 GHz ) slightly decreases with the increase of the bubble thickness. The 3dB-BW decreases to ~17 GHz when the bubbles are close to the size of the top mesa. However, the 3dB-BW drops drastically with the increase of the bubble thickness when the bubble radius reaches 7 μm. Mostimportantly, the 3dB-BW sharply decreases to ~30 MHz regardless of the thickness of the bubble when the bubble radius of 14 μm is set. This may provide guidance for the application of the wafer-bonded GeSn PIN PD.

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“…This is why capacitance levels are slightly increased by the increase of light power. The interface states density (denominated by D it or Nss) [92,93] is another highly important parameter for metal-semiconductor (MS, MOS, or MIS type) diodes and photodiodes, which parameter affects their performances. Different reasons such as impurities, crystal lattice vacancies, and voids can cause the presence of interface states.…”