Multiple-channel GaAs/AlGaAs high electron mobility transistors

Multiple-channel high electron mobility transistors (HEMTs) have been designed and fabricated on GaAs/AlGaAs heterostructural material grown by molecular beam epitaxy. The sheet carrier density of the two-dimensional electron gas measured at 77 K was linearly proportional to the number of high mobility electron channels, and reached 5.3 x 10 to the 12th/sq cm for six-channel HEMT structures. Depletion-mode devices of the double-heterojunction HEMT were operated between negative pinchoff voltage and forward-biased gate voltage without any transconductance degradation. A peak extrinsic transconductance of 360 mS/mm at 300 K and 550 mS/mm at 77 K has been measured for a 1-micron gate-length double-heterojunction enhancement-mode device. An extremely high drain current of 800 mA/mm with a gate-to-drain avalanche breakdown voltage of 9 V was measured on six-channel devices.