HIGH PERFORMANCE SUBMICROMETER ALINAS-GAINAS HEMT'S.

The performance of long-gate and short-gate Al//0//. //4//8In//0//. //5//2As-Ga//0//. //4//7In//0//. //5//3As HEMTs fabricated on high-quality MBE (molecular-beam-epitaxially)-grown material is discussed. The device structures were grown lattice-matched to semi-insulating InP substrates. The typical layer consisted of an AlInAs buffer, followed by an undoped GaInAs channel, a thin undoped AlInAs space, a doped AlInAs donor layer, an undoped AlInAs barrier layer, followed finally by an n** plus GaInAs cap layer. The two epitaxial layer designs (wafers A & B) investigated to date differed only in the GaInAs channel thickness, 80 nm for wafer A and 40 nm for wafer B. Devices with 1. 3- mu m gate length were fabricated on both wafers. Transconductances of over 465 mS/mm at 300 K were measured on several devices on both wafers. There was no strong correlation between the channel thickness and the I-V characteristics. Devices with approximately 0. 30- mu m gate length were fabricated on wafer A. They exhibited transconductances of over 650 mS/mm at room temperature. The maximum drain current density was approimately 600 mA/mm which is twice the current density obtainable from single heterojunction AlGaAs-GaAs devices. This predicts a high fan-out capability for AlInAs-GaInAs HEMTs.

Duke Scholars

Author April S. Brown Electrical and Computer Engineering