Keywords GaAs, III-V materials, HEMTs, JFETs
Start Date: 01-JAN-89 / Duration: 36 months
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The GIANTS project aimed to examine the high-speed performance of a number of GaInAs novel transistors. State-of-the-art circuits for IT systems were to be produced using those devices exhibiting the greatest performance potential and suitability for integration. GaInAs-based material structures were investigated because of their considerably superior transport properties compared to conventional GaAs structures (eg higher electron mobility and higher electron saturation velocity). These advantages are expected to lead to a new generation of high-speed devices and circuits.
The device types chosen for investigation were:
During the first phase of the project, the GIANTS team achieved rapid progress in all areas. Perhaps the most important area in the earlier stages was that of materials growth, and here progress was excellent. All partners and their associate partners met their first-year materials demonstrator targets, producing PMHEMT and LMHEMT wafers with state-of-the-art electrical performance parameters. In all cases progress was greatly helped by the assessment work carried out by Universidad Politecnica de Madrid on the partners' wafers.
The technology working group also achieved good progress. Thomson-CSF demonstrated 0.22 micron gate length pseudomorphic HEMT devices with f[t] values of up to 100 GHz and f[max] well in excess of 100 GHz. At 17 GHz these PMHEMTs exhibited noise figures of 0.9 dB with an associated gain of 11.3 dB. After producing 0.5 micron gate-length GaInAs JFETs with f[t]~57 GHz, LEP continued work on lattice-matched HEMTs with g[m] values up to 680 mS/mm for 0.6 micron gate length on MOCVD materials. Plessey completed the development of their baseline HEMT process, and made a second batch of pseudomorphic HEMT devices. These were fabricated on Picogiga material, and the 0.55 micron gate-length devices showed an extrinsic g[m] of 180 mS/mm, an f[t] of 27 GHz, and f[max] of approximately 55 GHz. In addition, a first batch of LMHEMTs was fabricated on in-house MOCVD material with excellent results. These 1.1 micron gate-length devices exhibited an extrinsic g[m] of 400 mS/mm, an f[t] of 24 GHz, and an f[max] of 56 GHz. STC made fully implanted InGaAs JFETs with g[m] values of 80-133 mS/mm and intrinsic f[t] values of 11.7 GHz for the 3 micron gate devices. STC's work on barrier-enhanced FETs also progressed well, with 1.5 micron gate devices fabricated with a g[m] of 150 mS/mm.
The theory working group produced an agreed set of parameters for InGaAs (strained and unstrained) including band offsets to GaAs, AlGaAs and InP, transport, and band structure parameters. Much of the fundamental analysis of these parameters was carried out at Lille, and the results used by the other group members. Lille, Plessey, Thomson-CSF and FORTH investigated the importance of quantum effects in the HEMT channel, and algorithms for the efficient computation of these effects were developed and compared. Initial models were completed for HEMT and JFET devices. FARRAN and STL used the agreed InGaAs data to attempt a first simulation of a JFET structure, and demonstrated the extreme sensitivity of the device performance to the precise implant profile.
In summary, all three working groups produced examples of novel GaInAs transistors with microwave performances approaching world records. These devices were compared at a later stage for their use in the project's final demonstrators:
The project was completed successfully with all the demonstrators established. These could later form the basis of the building blocks for specific IT subsystems.
Dr Ian Eddison
PLESSEY COMPANY PLC
Allen Clark Research Centre
UK - CASWELL, TOWCESTER NN12 8EQ
tel: + 44/ 327-54748
fax: + 44/ 327-53410
PLESSEY COMPANY PLC - UK - C
PHILIPS-LEP - F - P
PICOGIGA - F - P
THOMSON-CSF - F - P
BNR EUROPE LTD - UK - P
FORTH RESEARCH CENTRE - GR - A
UNIVERSIDAD POLITECNICA DE MADRID - E - A
UNIV. DES SCIENCES ET TECHNIQUES
DE LILLE-FLANDRES-ARTOIS - F - A
FARRAN TECHNOLOGY LTD - IRL - A
GIANTS - 2035, December 1993
please address enquiries to the ESPRIT Information Desk
html version of synopsis by Nick Cook