DOUBLE-HETEROJUNCTION LATTICE-MATCHED AND PSEUDOMORPHIC INGAAS HEMT WITH DELTA-DOPED INP SUPPLY LAYERS AND P-INP BARRIER ENHANCEMENT LAYER GROWN BY LP-MOVPE

In this letter we present for the first time a LP-MOVPE-grown double-heterojunction HEMT (DH-HEMT) with InP as carrier-supplying and barrier layers that avoid the kink effect due to Al-containing layers. A fully depleted p-InP barrier enhancement layer is used in order to increase the Schottky barrier. Lattice-matched (x = 0.53) and strained x = 0.68) InxGa1-xAs channels were investigated. The average maximum current I(DS(max)) for devices with 0.8-mum-long gates was very high for both cases (I(DS(max)) = 660 and 690 mA / mm for x = 53% and 740 and 950 mA / mm for x = 68%, respectively, at 300 and 77 K). For the same temperatures extrinsic peak transconductances g(mpeak) of 415 and 470 mS / mm (x = 53%) and 450 and 575 mS / mm (x = 68%) were measured. The average output conductance of the devices at g(mpeak) conditions was relatively low (g(ds) = 23 and 35 mS / mm at 300 K) and indicates a good confinement in the channel and the lack of kink effect. At room temperature and optimum conditions, gate-leakage currents of 0.7 mA / mm (x = 0.53) and 1 mA / mm (x = 0.68) were measured. The values of f(T) and f(max) at V(DS) = 2.5 V were 14.3 and 34.2 GHz for x = 53% and 17.2 and 45.2 GHz for x = 68%, respectively, at 300 K.