Deliverables
Facing the increasing interest in newer wide band-gap materials with their superior electronic properties including high breakdown electric field, high electron mobility and saturation carrier velocity, and high thermal conductivity, which can potentially fulfil power compounds requirements, "optimised gan power microwave devices on silicon" is the emerging solution for the need of more efficient components in the high voltage operation, high power density, low noise and linearity field.
This high performance technology added to the low cost issues are the opportunity for customer to establish as standards a reliable product at the forefront of the industry. For example, the immediate impact of power devices with low noise capabilities is an extreme competitive advantage by simplifying the transmission - reception chain by suppressing input protection in the wireless industry.
The introduction of these new family of compounds is therefore linked to price issues that have to be taken into account at the same level of the intrinsic performance of the material. Picogiga International is therefore appraising the MBE approach with all relevant issues coming from its history in the GaAs semiconductors industry.
The main activity has been focused on GaN/Si as targeted for Wireless communication (low cost issues) and preparing the next generation of material chain supply for High Performances materials in the electronic field.
At the end of the project the strategy of the Picogiga International confirms the establishment of a production pilote line for Nitride HFET on a multi - 4 wafer reactor as well as building alliances with customers to joint develop the next material chain supply for the Nitride material Industry.
Lumilog also grew HFETs structures on sapphire and 4H-SiC (SI) and obtained a very good homogeneity of the characteristics on the whole wafer and from wafer to wafer in the same run.
Low dislocation density GaN/sapphire templates with TDs density in the upper 107cm{-2} have been obtained improving the proprietary Si/N treatment of the sapphire substrate prior to the deposition of the low temperature buffer layer. These are pseudosubstrates to be used for the growth of nitride based device structure, like UV LEDs or FETs. These templates are also used as pseudosubstrates in MBE. One of our customers, Sharp UK, demonstrated the first MQWs GaInN/GaN laser diodes grown by MBE on Lumilogs GaN/sapphire templates.
ELO GaN/sapphire pseudosubstrates with TDs density between stripes in the mid 10-6cm{-2} are currently available. These are produced using the proprietary 2 step technology. These ELO pseudosubstrates are mainly used for the laser diodes fabrication.
GaN/sapphire templates with TDs density in the mid 108cm{-2} are currently available. These are produce using the proprietary Si/N treatment of the sapphire substrate prior to the depososition of the low temperature buffer layer. These are pseudosubstrate used for the growth of nitride based device structure, mainly in MBE where the current status of the technology does not allow fabricating low dislocation density templates.
Building on previous experience and know-how (in particular from EU JESICA), and other parallel efforts, NOVASiC succeeded in developing a reproducible SiC surface, yielding state-of-the-art epitaxial and device results. The StepSiC process provides atomic steps on on-axis SiC substrates. The StepSiC surface is also characterised by no scratches, low roughness, no damaged layer, low contamination. The benefit of this improved surface preparation on GaN growth was demonstrated by several partners and other SiC users worldwide.
A process for large volulme reclaim of SiC wafers is also operational, allowing scare material to be more available, and reducing dramatically material costs for the program.
As a result, NOVASiC is a steadily growing industrial and commercial operation, serving laboratories and industrial manufacturers around the world.
Thick GaN layer were grown by HVPE on ELO quality GaN/sapphire. Afterwards the starting sapphire was separated either by laser lift off or by a CNRS proprietary technology. These free- standing GaN exhibit TDs in the mid 106cm{-2} and therefore are suitable for the growth of laser diode structures.
The process still needs to improved (reduction of the pits density, of the bow, of the warp, polishing).
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