Carrier lifetime of GeSn measured by spectrally resolved picosecond photoluminescence spectroscopy
Brian Julsgaard, Nils von den Driesch, Peter Tidemand‐Lichtenberg, Christian Pedersen, Z. Ikonić, Dan Buca
Abstract
We present an experimental setup capable of time-resolved photoluminescence spectroscopy for photon energies in the range of 0.51 to 0.56 eV with an instrument time response of 75 ps. The detection system is based on optical parametric three-wave mixing, operates at room temperature, has spectral resolving power, and is shown to be well suited for investigating dynamical processes in germanium-tin alloys. In particular, the carrier lifetime of a direct-bandgap <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mi>Ge</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mi>Sn</mml:mi> <mml:mi>x</mml:mi> </mml:msub> </mml:mrow> </mml:math> film with concentration <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mi>x</mml:mi> <mml:mo>=</mml:mo> <mml:mn>12.5</mml:mn> <mml:mi>%</mml:mi> </mml:mrow> </mml:math> and biaxial strain <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mo form="prefix">−</mml:mo> <mml:mn>0.55</mml:mn> <mml:mi>%</mml:mi> </mml:mrow> </mml:math> is determined to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mn>217</mml:mn> <mml:mo>±</mml:mo> <mml:mn>15</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>ps</mml:mi> </mml:mrow> </mml:math> at a temperature of 20 K. A room-temperature investigation indicates that the variation in this lifetime with temperature is very modest. The characteristics of the photoluminescence as a function of pump fluence are discussed.