Gate Length Dependence of Large-Signal Output Characteristics for the MOSFETs in the Breakdown Region Using X-Parameter Model

In this letter, the gate length dependence of X₂₁₂₁^S and X₂₁₂₁^T intercept behaviors for the MOSFETs in the breakdown region is first analyzed using the X-parameter model. Shorter gate length decreases X₂₁₂₁^S coefficients and increases X₂₁₂₁^T coefficients at high drain voltage and high input power due to the significant RF avalanche effect in the high field region. X₂₁₂₁^S and X₂₁₂₁^T coefficients are determined using artificial neural network. Good agreement between the measured and fitted output scattering wave is achieved. The presented analysis for the gate length dependence X₂₁₂₁^S and X₂₁₂₁^T can be beneficial to CMOS power amplifier designs with the scaled-down MOSFETs.