Low-distortion MOSFET with optimized donor concentration profile at channel-drain junction designed by harmonic balance device simulation

Abstract

The nonlinear characteristics arising from the third-order intermodulation distortion (IMD3) of MOSFETs are investigated by harmonic-balance device simulation. First, to identify the spatial location in a MOSFET, where IMD3 is mostly generated, a conventional n-MOSFET structure is simulated, and it is found that IMD3 generation is located at the top surface over the channel-drain p-n junction where a high lateral electric-field exists. Second, to alleviate the impact of IMD3, we proposed and simulated three types of n-MOSFET structures with a low lateral electric-field around the channel-drain junction. We demonstrated that a low-distortion MOSFET can be realized by optimizing the doping concentration profile at the channel-drain junction. In particular, the introduction of a thin layer of a low-doped n-type surface-channel and a low-doped n-type drain at the top of p-type well and n-type drain regions resulted in a marked IMD3 reduction of as much as 8 dBm in IMD3 power characteristics, in comparison with a conventional structure.