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Compositionally graded buffers on GaAs as substrates for Al(0.48)In(0.52)As/Ga(0.47)In(0.53)As MODFETs

Gradierte Puffer auf GaAs als Substrate für Al(0.48)In(0.52)As/Ga(0.47)In(0.53)As MODFETs

Shur, M.S.; Suris, R.A.:
Compound Semiconductors 1996. Proceedings of the Twenty-Third International Symposium on Compound Semiconductors
Bristol: IOP Publishing, 1997 (Institute of Physics - Conference Series 155)
ISBN: 0-7503-0452-9
International Symposium on Compound Semiconductors <23, 1996, St. Petersburg>
Fraunhofer IAF ()
Epitaxie; epitaxy; high frequency field effect transistor; Hochfrequenz-Feldeffekttransistor; InGaAs/InAlAs MODFET

Ternary Al(0.48)In(0.52) As/Ga(0.47)In(0.53)As/Al(0.48)In(0.52)As MODFET structures on top of a buffer on GaAs substrate have been grown by molecular beam epitaxy. For a smooth transition between the lattice constants of the GaAs substrate and the MODFET epilayers, we investigated two compositionally graded buffer systems: adjustment of the new lattice constant in two distinct steps, or in a linear transition. On both buffer types, an identical MODFET structure was grown. Microwave transistors with 0.15 and 0.3 mu m gate length were fabricated using a well-established fully planar process. The device properties for the two structures were nearly identical; also, there was no significant difference to a reference structure grown lattice-matched on InP (g m,max=950-1150 mS/mm and f T=90-95 GHz for 0.3 mu m gate length). In addition, the MODFET structures grown on lattice-relaxed buffer layers on GaAs were tested with respect to their stability under FET operation as well as for temperatu re treatment at 250 deg C with no measurable degradation of device properties.