Integrated photonic circuits (PICs) operating at cryogenic temperatures are fundamental building blocks required to achieve scalable quantum computing, and cryogenic computing technologies 1,2. Silicon PICs have matured for room temperature applications, but their cryogenic performance is limited by the absence of efficient low temperature electro-optic (EO) modulation. Here we demonstrate EO switching and modulation from room temperature down to 4 K by using the Pockels effect in integrated barium titanate (BaTiO3)based devices 3. We investigate the temperature-dependence of the nonlinear optical (NLO) properties of BaTiO3, showing an effective Pockels coefficient of 200 pm/V at 4 K. The fabricated devices exhibit an EO bandwidth of 30 GHz, ultra-low-power tuning which is 10 9 times more efficient than thermal tuning, and high-speed data modulation at 20 Gbps. Our results demonstrate a missing component for cryogenic PICs. Our results remove major roadblocks for the realisation of cryogenic-compatible systems in the field of quantum computing, supercomputing and sensing, and for interfacing those systems with instrumentation at room-temperature. Cryogenic technologies are becoming essential for future computing systems, a trend fuelled by the worldwide quest to develop quantum computing systems and future generations of highperformance classical computing systems 4,5. While most computing architectures rely solely on electronic circuits, photonic components are becoming increasingly important (Supplementary Note, SN 1). First, PICs can be used for quantum computing approaches where the quantum nature of photons is exploited as qubits 1,2. Second, optical interconnects can overcome limitations in
Field effect induced luminescence has been achieved by alternate tunnel injection of electrons and holes into Si nanocrystals. The emitting device is a metal-oxide-semiconductor structure with a semitransparent polycrystalline Si contact ∼250nm thick and a silicon-rich silicon oxide layer of about 40nm deposited on a p-type Si substrate by plasma-enhanced chemical vapor deposition. The electroluminescence is optimized for a Si excess of 17% and annealing at 1250°C for 1h in nitrogen-rich atmosphere. The pulsed emission presents typical decay times of ∼5μs and external quantum efficiencies of ∼0.03%.
Abstract. An in-depth study of the physical and electrical properties of Sinanocrystals embedded in silicon dioxide is presented. These layers were fabricated with different Si concentrations by both ion implantation and plasma-enhanced chemical vapour deposition. Subsequently, LEDs devices based on a metal-oxide-silicon configuration with a ∼350 nm polycrystalline Si top electrode and an active layer of about 45-50 nm, were fabricated in conventional lithography process. In order to optimize the device performances, prior to the top electrode deposition, the structural and photoluminescent properties of the active layers were exhaustively studied.Devices fabricated by ion implantation exhibit a combination of direct current and field-effect luminescence under a bipolar pulsed voltages excitation. The onset of the emission decreases with the Si excess from 6 to 3 V. The direct current emission is attributed to impact ionization, and is associated with the reasonably high current levels observed in current-voltage measurements. This behaviour is in good agreement with transmission electron microscopy images that revealed a continuous and uniform Si-nanocrystals distribution. The emission power efficiency is relatively low, ∼10 −3 %, and the emission intensity exhibits fast degradation rates, as revealed from accelerated aging experiments.Devices fabricated by chemical deposition only exhibit field-effect luminescence which onset decreases with the Si excess from 20 to 6 V. The absence of the continuous emission is explained by the observation of a 5-nm region free of nanocrystals, which strongly reduces the direct current through the gate. The main benefit of having this nanocrystal-free region is that tunnelling current flow assisted by nanocrystals is blocked by the SiO 2 stack so that power consumption is strongly reduced, which in return increases the device power efficiency up to 0.1 % . In addition, the accelerated aging studies reveal a 50% degradation rate reduction as compared to implanted structures.PACS numbers: 73.63. Bd, 78.67.Bf, 85.60.Jb Submitted to: Nanotechnology Si nanocrystal-based LEDs fabricated by ion implantation and PECVD 2
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