Cutting edge transistor technology
The DENIS project, comprised of leading European Institutions and semiconductor engineering specialists, has fabricated gallium nitride (GaN) wafers that can be used for the production of high quality transistors. Two different approaches were followed. In the first, metaloorganic vapor phase epitaxy (MOVPE) was utilized and GaN substrates were grown by hydride vapor phase epitaxy (HVPE). This way, the wafer produced exhibits physical properties, like electron mobility and carrier concentration, suitable for high performance high electron mobility transistors (HEMTs). After processing the wafer, the resulting transistor with AlGaN barriers, was extensively tested and showed parameters comparable to transistors fabricated by the leading US and Japanese manufacturers. Moreover the sophisticated epitaxial techniques used facilitated the production of wafers with reproducible and tunable physical properties, an element of critical importance for future commercial production. The second, equally novel approach consisted of molecular beam epitaxy (MBE) growth technique for the preparation of GaN/AlGaN heterostructures. Here bulk gallium nitride dopped with magnesium was used as a substrate. The outcome was quite spectacular and unexpected, namely record mobility structures were achieved. Such structures will open up new pathways in basic research of various exciting phenomena. Already new effects are expected in the Quantum Hall Effect regime. The techniques developed will now boost nitride technology in Europe and in the near future it is highly expected that from laboratory the consortium will move to commercial production since both techniques are reproducible and scaleable.
