The effectiveness of fluorine incorporation control for reliability improvement of the AlInAs/GaInAs high electron mobility transistor (HEMT) is demonstrated. The inverted-type HEMT ( HEMT) is found to be one of the feasible structures. In this structure, the GaInAs channel layer functions as a blocking layer against the thermal diffusion of fluorine into the AlInAs electron supply layer, which is a main cause of the electrical deterioration in the HEMT material. Under de operation at an ambient temperature of 170 degrees C, the zero-gate-bias saturated drain current of the i-HEMT decreases only a few percent even after 3,500 h. The projected median-time-to-failure of the i-HEMT is estimated to be 10(7) h at a temperature of 125 degrees C, which is almost twice that of the conventional-type AlInAs/GaInAs HEMT.