30 GHz GeSn photodetector on SOI substrate for 2 µm wavelength application
Xiuli Li, Linzhi Peng, Zhi Liu, Zhiqi Zhou, Jun Zheng, Chunlai Xue, Yuhua Zuo, Baile Chen, Buwen Cheng
Abstract
We report the demonstration of a normal-incidence p-i-n germanium-tin ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>Ge</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.951</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>Sn</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.049</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) photodetector on silicon-on-insulator substrate for 2 μm wavelength application. The DC and RF characteristics of the devices have been characterized. A dark current density under <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mo form="prefix">−</mml:mo> <mml:mn>1</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> </mml:math> bias of approximately <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mn>125</mml:mn> <mml:mtext> </mml:mtext> <mml:mtext>mA/</mml:mtext> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> is achieved at room temperature, and the optical responsivity of 14 mA/W is realized for illumination wavelength of 2 μm under <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mo form="prefix">−</mml:mo> <mml:mn>1</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> </mml:math> reverse bias. In addition, a 3 dB bandwidth ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m5"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>f</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>dB</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) of around 30 GHz is achieved at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m6"> <mml:mrow> <mml:mo form="prefix">−</mml:mo> <mml:mn>3</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> </mml:math> , which is the highest reported value among all group III–V and group IV photodetectors working in the 2 μm wavelength range. This work illustrates that a GeSn photodetector has great prospects in 2 μm wavelength optical communication.