Reliable Fabrication of Electrically Tunable Quantum Dot Emitters on SiN via Micro-Transfer Printing

Many applications in quantum communication and information processing demand integrated and tunable quantum emitters within a low-loss, scalable platform that can support multiple devices. While state-of-the-art In(Ga)As quantum dot devices have been realized in GaAs platforms[I], they suffer from significant propagation losses, typically on the order of 10 dB/mm. In this work, we integrate such electrically tunable p-i-n GaAs devices into a low-loss SiN platform. For this, we fabricated suspended GaAs devices, encapsulated in photoresist coupons on their native source wafer. Using a commercial micro-transfer printer, we reliably integrated these on the SiN platform. Afterwards, the photoresist encapsulation was removed prior to final metallization. This approach led to a high fabrication yield of 94.7%, with 36 out of 38 devices successfully integrated. After wirebonding the parallel-connected devices, the sample was mounted into a 4 K cryostat. Upon cooldown, the devices demonstrated consistent GaAs/SiN coupling efficiencies on the order of 1 dB, enabling the characterization of quantum dot emission using both GaAs and SiN grating couplers. In Fig. 1(b), when sweeping the voltage across the p-i-n diodes in forward bias under above-band excitation at 800 nm, the quantum dot spectral lines exhibit the expected quadratic response, which is consistent with the quantum confined Stark effect. After inserting an ultra-narrowband optical filter to select a single emission line, we characterized the emitted photon purity in second-order photon correlation measurements under p-shell excitation. In Figs. 1 (c-d), we observe a clear antibunching dip, corresponding to a raw <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$g^{2}(\tau=0)$</tex> of 7.02 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm$</tex> 1.29%. At longer timescales, we observe a blinking effect that essentially disappears under low excitation powers, clearly demonstrating the supression of charge noise.