Metamorphic HFETs with composite In0.8Ga0.2As/InAs/In0.8Ga0.2As channels on GaAs substrate

Metamorphic HFET materials with InAs/In(0.8)G(0.2)As channels have been grown on GaAs substrates. The influence of the insertion of an InAs layer has been investigated regarding the thickness and the position of the layer. The insertion of InAs results in 20 % increase in electron mobility at room temperature (34 % at 77 K). HFETs with 0.3 mu m gate length have been fabricated and characterized. An extrinsic DC transconductance of 1100 mS/mm was achieved. Excellent high frequency performance has been achieved at low voltages. An f(max) of 100 GHz and an f(T) of 100 GHz were achieved at a drain voltage of 0.25 V and 0.75 V respectively. The f(T).l(g) product of 30 GHz.mu m corresponds to a carrier velocity of 1.9.10(7) cm/s. The minimum noise figure was 0.8 dB with an associated gain of 9.2 dB at 25 GHz.