Horizontal GeSn/Ge multi-quantum-well ridge waveguide LEDs on silicon substrates
Linzhi Peng, Xiuli Li, Zhi Liu, Xiangquan Liu, Jun Zheng, Chunlai Xue, Yuhua Zuo, Buwen Cheng
Abstract
A horizontal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mi mathvariant="normal">p</mml:mi> <mml:mo form="prefix">−</mml:mo> <mml:mi mathvariant="normal">i</mml:mi> <mml:mo form="prefix">−</mml:mo> <mml:mi mathvariant="normal">n</mml:mi> </mml:mrow> </mml:math> ridge waveguide emitter on a silicon (100) substrate with a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>Ge</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.91</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>Sn</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0.09</mml:mn> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mi>Ge</mml:mi> </mml:mrow> </mml:math> multi-quantum-well (MQW) active layer was fabricated by molecular beam epitaxy. The device structure was designed to reduce light absorption of metal electrodes and improve injection efficiency. Electroluminescence (EL) at a wavelength of 2160 nm was observed at room temperature. Theoretical calculations indicate that the emission peak corresponds well to the direct bandgap transition ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:msub> <mml:mi>n</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mi mathvariant="normal">Γ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>−</mml:mo> <mml:msub> <mml:mi>n</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mi>H</mml:mi> <mml:mi>H</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ). The light output power was about 2.0 μW with an injection current density of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mn>200</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>kA</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . These results show that the horizontal GeSn/Ge MQW ridge waveguide emitters have great prospects for group-IV light sources.