CIFRE - Développement de DHBT GaInP​/GaAsSb et InP​/GaAsSb DHBTs sur GaAs; F​/H

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The bipolar heterojunction transistors (HBT) on GaAs substrates, used today in mobile phone power amplifiers at frequencies of a few GHz, have limited gain at higher frequencies, particularly in the 6G FR3 band (7-24GHz). Gallium arsenide antimonide (Ga As Sb ) double-heterojunction bipolar transistors (DHBT) on InP substrates currently represent the state of the art in frequency performance, with a maximum oscillation frequency f MAX >

1 THz, enabling them to address high-frequency applications as well as high-speed optical communications. However, the use of an InP substrate, which is a fragile, scarce and therefore expensive material, is a drawback of these transistors. This thesis aims to investigate the potential of pseudomorphic GaInP/Ga As Sb  DHBTs on GaAs substrates, as well as metamorphic InP/Ga As Sb  DHBTs on GaAs substrates.

• DHBTs pseudomorphic GaInP/Ga As Sb /GaAs.
  • Start with a mapping of the Ga As Sb  composition parameter space as a function of thickness for pseudomorphic growth (the literature provides initial guidance).
  • Identify layer stacks that can be achieved by epitaxy.
  • Fabricate DHBTs with the highest possible performance by adapting the existing Ga As Sb /InP DHBT fabrication process and reducing the dimensions as much as possible.
• DHBTs metamorphic InP/Ga As Sb /GaAs.
  • Transfer the InP/Ga As Sb  DHBT process developed at ETH Zurich to a metamorphic platform with thin bases and collectors and fine geometries.
  • Evaluate the effect of residual dislocations on device yield.
  • Assess the impact of the metamorphic buffer and its thermal conductivity on RF performance and compare it with the native InP-based technology.

• You hold an engineering degree or a Master's degree (Master
  2).
• You have a strong command of semiconductor material and device physics and very good knowledge of the associated fabrication processes.
• Ideally, you have knowledge of heterojunction bipolar transistors.
• You have at least a B2 level in English.
• You are rigorous, dynamic, motivated, with strong analytical skills to solve problems and the ability to synthesize scientific work.
• You enjoy working in a team.

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