Description of Work packages

Overview

WP1 aims at providing, characterising and improving the material quality of the starting materials, which are 2” SiC single crystal, Si single crystals and polycrystalline SiC (pSiC) wafers. The second objective of this work package is to reduce the material cost by increasing growth rate and diameter from 2” to 4”, and to improve the growth yield.

The most innovative aspect of the present project concerns the assessment of composite substrates for III-N materials dedicated to high power application. Therefore four objectives have been identified in WP2 (composite structures):

• Models investigating the thermal budget behaviour related to the compound devices and starting materials.
• 4” diameter, mature Si substrates and low cost perspectives associated with the emerging demand in scalability of high power device.
• Maintain the quality of epitaxial layers resulting from a better lattice match with the GaN family materials.
• Development of an interactive characterisation to qualify the various stages realised in the experiments.

Epitaxy work in WP 3 is the next decisive step in the validation of composite substrates. In many of the future high performance applications of the new composite substrates, epitaxial layers will have to be grown on the substrate to constitute the device active layer. Because the growth of III-N compounds and hetero-structures having to be re-optimised for any new type of substrate, and in particular on the composite substrates developed in the HYPHEN project, three objectives have been identified:

• Validate the epitaxy of III-N compounds on the composite substrates Si/pSiC and SiC/pSiC,
• Evaluate the crystal quality of the compound substrates through III-N epilayers grown on them,
• Evaluate the composite substrates quality at the user’s level, by providing GaAlN/GaN HEMT complete hetero-structures to be processed into test devices, which can be directly compared to devices on bulk single crystal substrates.

WP4 on Device Process is necessary to get information on the composite substrate quality as seen from the device manufacturer’s point of view. It is the next stage after the material characterisation work, which will be performed in WP2 and WP3. One main goal of this work package will be to set up the basis of a fabrication process adapted to the exploratory substrates.

The main goal of WP5 Assessment is to provide feedback information to the previous work packages: composite substrate fabrication in WP2, epitaxy in WP3, and wafer processing in WP 4, in order to allow the optimisation of the fabrication process at each level. The focus will be put on the comparison between the characterisation results obtained on reference wafers on silicon and SiC bulk substrates, processed in the frame of other programs outside this project, and composite substrates processed in WP4 As much as possible, we will try to set up and validate methods for to correlate the device electrical characteristics with the substrate material properties.

PERT diagram