Electroluminescence as an instrument to observe defect generation in InGaP/GaAs HBTs

The usage of electroluminescence for investigating the reliability of GaAs based HBTs has been reported previously (Henderson, 1995, Harris et al., 1998). Electroluminescence is the emission of photons generated by recombination of electrons and holes near a p/n junction at a heterointerface. This technique is commonly used in optoelectronics for determining reliability and robustness of light emitting diodes (LEDs) and semiconductor lasers. Dislocations and defects were observed as dark lines, so called DLDs, in HBTs (Henderson, 1995) and LED/LDs as a result of electroluminescence imaging of degraded devices. The authors use this technique to observe the generation of defects in InGaP/GaAs heterojunction bipolar transistors (HBTs) with an MTTF of more than 2 times 10⁷ h during reliability investigations. All reliability tests were carried out on multi-finger microwave power HBTs fabricated at the Ferdinand-Braun-Institut