| Abstract: | This paper reports the present status of GaAs based-heterojunction bipolar transistor (HBT) under development at Thales. We have developed a complete GaInP/GaAs-based technological process from material studies to discrete devices and microwave monolithic integrated circuits (MMIC) realisations. This know-how has been transferred recently to Thales/United monolithic semi-conductors. Discrete devices with output power over 1 W and power added efficiency (PAE) over 50% have been obtained at 10 GHz in CW. 8 W MMIC amplifiers have been fabricated using the same unit cells. The first reliability results are promising: more than 6000 h without failure for devices stressed up to 210°C and 40 kA cm−2. However, it seems that these results can still be improved. Some physical properties of the GaInP/GaAs HBT structures are suspected to have a major impact on the device reliability. The role of key parameters such as hydrogen incorporation in the GaAs base layer or residual strain in the GaInP/GaAs HBT structure has been investigated and its effects on the device characteristics identified. However, the major reliability improvement came from a novel way to passivate the extrinsic base surface. A comparison of the obtained results (device performance and reliability) with some of the best reported values in the literature (HP, TI, Daimler-Benz, etc.) is presented. |
