Zuverlässigkeitsuntersuchung von GaAs Heteroübergang- Bipolartransistoren (Volume 12) (English shop)

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This work investigated the reliability of high-frequency GaAs heterojunction bipolar transistors (HBTs) fabricated at the Ferdinand-Braun-Institut for applications with high reliability requirements (mobile communications, space). For the lifetime investigations, reliable measurement equipment and the corresponding methodologies were developed and established. The investigations were carried out in parallel with the technology development in order to examine the influence of variations in the technology parameters on the lifetime of the HBTs and to provide corresponding feedback to the technology. In addition, analytical investigations were performed on degraded HBTs in order to identify and characterise weak points and the degradation mechanisms responsible for failures. Using physical analysis methods (SEM, FIB, TEM, EL), the main degradation mechanism could be identified and the resulting defects made visible and characterised.

The determination of the median lifetime of the HBTs within a reasonable period of time was carried out by accelerating the ageing through an increase in the ambient temperature and the collector current density. Supporting the development of the HBTs with reliability investigations led to an increase in the median lifetime to 1.1×10⁷ hours, which exceeds the requirements by an order of magnitude. These values are among the best published values, even though they were achieved at significantly higher current densities, which testifies to the particular reliability of these devices.