Material Development of Antimonide Low-Noise Amplifiers for Qubit Read-Out

The read-out of qubits operating at cryogenic temperatures is a real challenge [1]. A key component in the amplification chain (figure c) of the weak signals is a low-noise amplifier (LNA) with the highest possible signal-to-noise ratio and operating below 4 Kelvin. An additional crucial requirement for the LNA is low power dissipation due to the limited cooling power of cryostats. III-V high electron mobility transistors (HEMT, sketch in figure b) are the superior technology meeting these requirements.

Nano-ridge engineering (NRE) [2] is a unique monolithic integration approach introduced by imec to fabricate high-quality III-V devices on Si substrates from nano-ridges (example in figure a). This hetero-epitaxial concept is based on selective area growth by metal-organic vapor phase epitaxy (MOVPE). The monolithic integration starts with the III-V deposition inside deep narrow oxide trenches, fabricated on a Si substrate. The growth in these high aspect ratio trenches ensures efficient trapping of misfit defects caused by lattice mismatch between III-V materials and Si, resulting in high III-V crystal quality. Once the trenches are filled, the crystal continues to grow outside of the trench where the nano-ridge shape and size control is achieved by manipulating the MOVPE growth conditions. NRE is successfully demonstrated for GaAs, GaSb and InGaAs [3][4]. Various devices such as heterojunction bipolar transistors [5], lasers [6] and photodetectors [7] were already demonstrated, emphasizing the large potential of this approach.

The topic of this PhD project is the development of state-of-the-art NRE based hetero-structures exploring different antimony-based III-V alloys, e.g., GaAsSb, GaPSb, InPSb, as barrier layer for a InAs channel HEMT with a clear focus on low-noise, high speed and low operating power of the device.

During your PhD you will

• Design and execute growth experiments on MOVPE reactors (lab tool and industrial 300 mm tool) and understand the physics and thermodynamics behind the deposition process
• Carry out device processing
• Master structural and electrical characterization techniques
• Acquire knowledge on defect formation in the grown 3D nano structures
• Interpret the analysis results of your device samples and relate your observation with device modelling
• Gain insight in the HEMT device physics and electrical characterization.

You will join imec’s Materials and Interfaces, Deposition and Analysis (MIDA) department and benefit from its strong expertise in thin film deposition and epitaxy. Your PhD research will take place at the interface of science and industrial innovation, with access to imec’s state-of-the-art cleanroom and characterization labs. You will enrich your competences via the KU Leuven PhD trajectory and the imec academy. You will share your results with industrial partners and the international research community and be part of a vibrant MIDA PhD community of around 30 students supported by scientists, engineers, staff, and professors.

[1] J.M. Hornibrook et al., “Cryogenic Control Architecture for Large-Scale Quantum Computing”, Phys. Rev. Applied, vol. 3, 024010, 2015.

[2] B. Kunert et al., “Gaining an edge with nano-ridges”, Compd. Semiconductor, vol. 24, no. 05, pp. 36–41, 2018.

[3] M. Baryshnikova et al., “Nano-Ridge Engineering of GaSb for the Integration of InAs/GaSb Heterostructures on 300 mm (001) Si”, Crystals, vol. 10, no. 4, p. 330, 2020.

[4] B. Kunert et al., “Application of an Sb Surfactant in InGaAs Nano-ridge Engineering on 300 mm Silicon Substrates”, Cryst. Growth Des., vol. 21, no. 3, pp. 1657–1665, 2021.

[5] A. Vais et al., “First demonstration of III-V HBTs on 300 mm Si substrates using nano-ridge engineering”, 2019 IEEE International Electron Devices Meeting (IEDM), 9.1.1-9.1.4, 2019.

[6] Y. De Koninck et al., “GaAs nano-ridge laser diodes fully fabricated in a 300 mm CMOS pilot line”, Nature, vol. 637, p. 63-69, 2025.

[7] C. I. Ozdemir et al., “Low Dark Current and High Responsivity 1020nm InGaAs/GaAs Nano-Ridge Waveguide Photodetector Monolithically Integrated on a 300-mm Si Wafer”, J. Light. Technol., vol. 39, no. 16, pp. 5263–5269, 2021.