Thick-Strained-Si/Relaxed-SiGe Structure of High-Performance RF Power LDMOSFETs for Cellular Handsets

A strained-Si/relaxed-SiGe structure was applied to laterally diffused MOSFETs (LDMOSFETs) in order to improve the PAE of cellular handset RF power-amplifier applications. The LDMOSFETs were fabricated in a 70-nm-thick strained-Si/relaxed-Si
_0.85
Ge
_0.15
structure. Despite the appearance of misfit dislocations, the thick strained-Si was essential for high efficiency and low leakage. The self-heating effects on the power performance were estimated to be negligible by using dynamic thermal simulation. The devices exhibited 46.6% PAE at a P
_out
of 27.5 dBm for wideband code-division multiple-access handset applications, which was a 3.8-point improvement over Si controls