Programme:  Applied Research Programme supported by the National Centre for Research and Development

Project co-ordinator:  Institute of Electron Technology, Warsaw

Starting date:   01.11.2012
Duration:   36 months
Participants:  Institute of Electron Technology
Institute of Physics Polish Academy of Sciences
Warsaw University of Technology
Institute of High Pressure Physics Polish Academy of Sciences
Ammono S.A.
TopGaN Sp. z o.o.

Project aim

The objective of this project is to research and develop a new type of microwave S band HEMT (High Electron Mobility Transistor) based on novel AlGaN/GaN heterostructures grown on bulk monocrystalline semiinsulating GaN substrates. The substrates will be fabricated by ammonothermal method and their size scaled for 1” to 1.5”. Two techniques - MOVPE and MBE will be used for the epitaxial growth of HEMT structures with high concentration and high mobility electron 2D gas, and improved structural quality. The fundamental approach behind the workplan is based upon the interaction between four key technical areas of expertise:

1. HEMTs modeling and design, 
2. material growth and characterisation, 
3. devices fabrication and
4. packaging and chip assessment.

A number of specific processing steps will be optimised including the definition of the active device area, RIE/ICP etching for ohmic contacts and gate recessing, through wafer via holes fabrication. Reliability issues will be of particular concern.

Key issues

One of the main issues in GaN-based HEMT technology is the lack of a lattice-matched semiconductor substrate. At the moment the best results in demanding radio frequency (RF) applications are obtained using SiC substrates. Alternatively, for less demanding applications Si substrates are used for HEMT structure growth. A significant problem arising with the application of non native substrates is the degradation of HEMT structures under high load conditions (i.e. high voltage bias resulting in the creation of high electric fields in the active structure) due to a high defect density in such epitaxial structures (most importantly in the buffer layer but also in the AlGaN barrier layer yielding charge trapping in the HEMT channel region). Further complex issues in the structurisation and mounting arise. We expect, that the research strategy of the project will enable to develop a fully nitride AlGaN/GaN HEMT technology using free-standing GaN substrates yielding a significant increase in long term reliability of the transistors.

High level of R&D activities

Poland has long been known as a country of origin of some of the most significant R&D institutions and companies in the film of GaN-based electronics. This project is based on the cooperation of the leaders in the field, in particular AMMONO S.A. specializing in bulk GaN crystal growth using ammonothermal growth yielding state-of-the-art crystal quality as well as TopGaN specializing in MOVPE nitride epitaxy used in HEMT structure growth in particular known for their blue optoelectronic devices. The processing of the transistors will be carried out by the Institute of Electron Technology using technology developed as a result of R&D works carried out since 2004 under several EU Framework Programmes and National Cohesion Strategy Programmes. Institute of High Pressure Physics PAS and Institute of Physics PAS bring into the project their unique expertise on the physics of the material as well as on MBE growth of the nitride structures and Institute of Radioelectronics of the Warsaw University of Technology, a worldwide recognized expert on the design and implementation of high power high frequency amplifiers will be responsible for the characterization and specification of the completed transistors.

Expected project impact

The HEMT realized in the frames of the project will target the needs of polish defense and civilian industry, in particular the polish radiolocation industry based on the 50 years of experience of PIT and RADWAR (currently in the BUMAR consortium). The development and future implementation of microwave high power HEMT transistors on GaN substrates will be a world-class achievement in semiconductor technology. It will form a relevant basis for simultaneous work on high power electronics, in particular for energoelectronic systems as well as for green technology systems (concerning renewable energy sources and hybrid vehicles). Another potential application area is the one of harsh environmental sensors working at high temperatures and in corrosive environments.

1. PRESENTATION: Pol-HEMT: AlGaN/GaN microwave HEMT transistors on monocrystalline GaN substrates, PDF document, version 1.7, 5MB

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