Measurement methods for accurate microwave characterization and modeling of MESFET chips

The subject of accurate measurement and modeling oof three-terminal chip devices such as bipolar junction and field-effect transistors has been addressed by others with varying degrees of success. This paper discusses a two-tier approach for determining highly accurate wide-band scattering parameters of chip GaAs MESFETs that are referenced at the bonding pads of the device. In a two-tier approach the first level of characterization determines error corrections for a measurement system. The second level is characterization of any test fixture used in the measurement of the device. The discussion is directed at the second level of characterization in which methods of one-port untermination and deembedding are extended to two-port measurements and a technique known as cold chip parasitic error correction is introduced which makes possible acurate placement of the S-parameter reference planes at the terminals on the chip device. Microwave modeling of the GaAs MESFET can be approached for two different directions, that of device physics and that of device measurements. This paper examines two different measurements-based modeling methods in which accurate chip level S-parameter data is a necessity.