Title :
High-frequency SiGe-n-MODFET for microwave applications
Author :
Zeuner, M. ; Hackbarth, T. ; Hock, G. ; Behammer, D. ; Konig, U.
Author_Institution :
Daimler Chrysler Res. Center, Ulm, Germany
Abstract :
n-type SiGe modulation-doped hetero field-effect transistors (MODFET´s) with a 0.25-μm Schottky-gate on a Si/sub 0.55/Ge/sub 0.45/ buffer are presented. The layer structure was designed to enable elevated sheet carrier densities of n/sub s/=7.0×10/sup 12/ cm/sup -2/ at moderate electron mobilities of 1050 cm2/Vs. Reducing the thickness of the cap layers enhances the control of the gate on the 2DEG and leads to a high transconductance of 320 mS/mm. Targeting analog applications, we focused on large current densities around 400 mA/mm. Due to advanced RF-characteristics the 100-GHz hurdle of fmax was passed for the first time with fmax(U)=120 GHz and fT was determined at 42 GHz.
Keywords :
Ge-Si alloys; carrier density; current density; electron mobility; equivalent circuits; high electron mobility transistors; microwave field effect transistors; semiconductor device models; semiconductor materials; two-dimensional electron gas; 0.25 micron; 120 GHz; 2DEG; 320 mS/mm; 42 GHz; Schottky-gate; Si-Si/sub 0.55/Ge/sub 0.45/; SiGe-n-MODFET; current densities; electron mobilities; elevated sheet carrier densities; field-effect transistor; microwave applications; modulation-doped FET; n-type SiGe; transconductance; Charge carrier density; Electron mobility; Epitaxial layers; FETs; Germanium silicon alloys; HEMTs; MODFETs; Silicon germanium; Thickness control; Transconductance;
Journal_Title :
Microwave and Guided Wave Letters, IEEE
