Characteristics of GaAs HEMTs with Flip-Chip Interconnections

A GaAs HEMT with flip-chip interconnections has been developed. There are various ground current passes for the HEMT on surface of the GaAs chip in this assembly structure, each pass depending on the transmission line type for the chip. We evaluated the high-frequency characteristics of the HEMT TEGs with flip-chip interconnection for three types of the transmission lines: with a microstrip line (MSL), with a coplanar waveguide (CPW), and with an inverted microstrip line (IMSL). All three types of TEGs had similar values of a maximum available power gain (MAG) at 30 GHz. However, the IMSL-type TEG, which had superior characteristics in high-frequency ranges of more than 30 GHz, was chosen as the most suitable type. The IMSL-type TEG had an MAG of 10.02 dB and a Rollett stability factor K of 1.20 at 30 GHz.