ABSTRACT
In this work, we present the 0.1pm GaAs PHEMT with InGaAs layer and Si pulse doped cap layer to improve ohmic contact, which demonstrated an ohmic contact resistance of 0.07Q-mm
2. Epitaxial structure This work deals with the double Si pulse doped Al0.22GaAs/In0.22GaAs PHEMT grown by molecular beam epitaxy (MBE) on a GaAs substrate, yielding a mobility of 5,650cm12/V-s and a sheet carrier density of 4x l0 12/cm2 at 300K. In order to get high performance in the W-band, it is necessary for gate length of device to be reduced to 0.1pm. Therefore parasitic source resistance is not negligible any more in 0.1pm device. To get low source resistance and low-resistance ohmic contact, we adopted the cap layer
consisted of InGaAs contact layer and Si pulse dope donor layer. This cap structure leads to facilitate the current flow across the metal-semiconductor interface by field emission. The cap layer was grown sequentially : 20nm Si doped ( lx l0 18cm 3) GaAs layer, 12nm Si doped (6xl0 18cm'3) GaAs layer, Si pulse dope (6x l0 ,2cm'2 ) layer, and 8nm Si doped (3xl019cm 3) InGaAs contact layer. A schematic cross-section of the epitaxial structure is shown in Fig.l. in0?:GaAs | CaD 3X10 '9cm '3 80A
Figure 1. Schematic of GaAs PHEMT .
