2.2 High Electron Mobility Transistors

In terms of industrial production, HEMTs challenge the MESFETs due to their superior transport properties. This leads to higher gain, higher power added efficiency (PAE), higher output power, and better low noise properties for a larger frequency range available up to 215 GHz, demonstrated in MMICs [313]. Fig. 2.1 and Fig. 2.2 compare the output power and the output power density for pseudomorphic AlGaAs/InGaAs HEMTs, InAlAs/InGaAs HEMTs on InP and GaAs-Metal Semiconductor Field Effect Transistors (MESFETs). In Fig. 2.3 and Fig. 2.4, the gain per stage and the PAE are compared.

Figure 2.1: Comparison of saturated output power/mm gate width as a function of frequency.

Figure 2.2: Comparison of the absolute output power as a function of frequency.

Figure 2.3: Comparison of gain per stage as a function of frequency.

Figure 2.4: Comparison of the power added efficiency as a function of frequency.