Quantum dots on GaAs substrates as integration-ready high-performance single-photon sources at telecommunication wavelengths

The development of deterministic single-photon sources emitting in the telecommunication bands is a key challenge for quantum communication and photonic quantum computing. Here, we investigate the optical properties and single-photon emission of molecular beam epitaxy (MBE) grown semiconductor quantum dots (QDs) emitting in the telecom O- and C-bands. The QDs are embedded in an <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi>In</a:mi> <a:mi>Ga</a:mi> <a:mi>As</a:mi> </a:mrow> </a:math> matrix with fixed indium content grown on top of a compositionally graded <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mi>In</c:mi> <c:mi>Ga</c:mi> <c:mi>As</c:mi> </c:mrow> </c:math> buffer. This structure allows for the future implementation of electrically contacted nanocavities to enable high-quality and bright QD emission. In detailed optical characterizations we observe linewidths as low as <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mn>50</e:mn> <e:mspace width="0.2em"/> <e:mtext fontfamily="times">μ</e:mtext> <e:mi>eV</e:mi> </e:math> , close to the spectrometer resolution limit, low fine structure splittings close to <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mn>10</i:mn> <i:mspace width="0.2em"/> <i:mtext fontfamily="times">μ</i:mtext> <i:mi>eV</i:mi> </i:math> , and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:msup> <m:mi>g</m:mi> <m:mrow> <m:mo stretchy="false">(</m:mo> <m:mn>2</m:mn> <m:mo stretchy="false">)</m:mo> </m:mrow> </m:msup> <m:mo stretchy="false">(</m:mo> <m:mn>0</m:mn> <m:mo stretchy="false">)</m:mo> </m:math> values as low as <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"> <s:mn>0.08</s:mn> </s:math> . These results advance the current performance metrics for MBE-grown QDs on <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"> <u:mrow> <u:mi>Ga</u:mi> <u:mi>As</u:mi> </u:mrow> </u:math> substrates emitting in the telecom bands and showcase the potential of the heterostructures presented for further integration into photonic devices.