Investigation of Ga doping behavior during low temperature epitaxy

More than two weeks ago

Next MOS devices need an increase in active doping concentration in the Source/Drain layers. Adding Ga to boron doped SiGe might do the job.

Epitaxial growth of group IV materials is a well-known process, used at many different steps during the production of a wide range of semiconductor devices ranging from lasers to MOSFETs. Epitaxial Si is a base for the production of practically every chip. SiGe is responsible for success of both high frequency BICMOS and highly scaled CMOS transistors.

At present, most of the major semiconductor players produce chips on the fin FET technology at the 14-10 nm technology node with 7 nm beeing around the corner. It is also often considered that devices at 7 and 5 nm or even smaller nodes will be based on alternative group IV semiconductors (SiGe, Ge). SiGe and Ge, contrary to Si allow to improve electrical characteristics of pMOS transistors due to higher intrinsic holes mobility.


Although conventional growth of group IV materials on Si is well known, new device architectures (finFETs, gate all around FETs, nanowire FETs, etc) impose very stringent requirements on composition, doping, thermal budget, etc. In many cases epitaxial material has to be grown at temperatures which are too low for conventional precursors used in the semiconductor industry (silane, dichlorosilane, germane) resulting in very low deposition rates. Increase of temperature often leads to changed devices geometry and loss of performance.

In order to solve the problems mentioned above, high order germanes and silanes receive lately considerable attention. Non selective processes based on such precursors have been developed and are used for the production of  nanowire FinFET devices, electro absorption modulators and memory devices. The next step is to investigate possibilities for doping and growth selectivity in order to develop processes suitable for application on patterned wafers.


The aim of this work will be to study the epitaxial growth of SiGe:Ga using advanced precursors for epitaxy and Ga as a new doping element. The main focus will concern the growth kinetics, structural and electrical properties of the obtained layers.


The candidate is expected to:

  • focus on the epitaxial growth aspects and study the physics and chemistry involved in the CVD of group IV materials using high-order silanes and germanes;
  • investigate epitaxial material properties, characterize defects and study their electrical activity;
  • learn and master characterization techniques such as X-ray diffraction, micro 4-point probe, SEM,SIMS, etc.

Type of project: Combination of internship and thesis

Duration: 6 months

Required degree: Master of Engineering Technology, Master of Science, Master of Engineering Science

Required background: Physics, Nanoscience & Nanotechnology, Materials Engineering, Electrotechnics/Electrical Engineering

Supervising scientist(s): For further information or for application, please contact: Clement Porret ( and Andriy Hikavyy (

Imec allowance will be provided for students studying at a non-Belgian university.

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