A comprehensive study of AlGaAs/GaAs beryllium- and carbon-doped base heterojunction bipolar transistor structures subjected to rapid thermal processing

AlGaAs/GaAs single heterojunction bipolar transistor (HBT) structures with Be- and C-doped bases have been annealed at different temperatures using ra pid thermal processing (RTP). Both electrical and low-temperature photolumi nescence measurements were used to investigate their thermal stability. We found that the conventional AlGaAs/GaAs abrupt HBT structures could undergo significant degradation at temperatures commonly encountered in typical RT P for device fabrication. The decrease of current gain was observed in both molecular beam epitaxy-grown HBTs with a Be-doped base and metalorganic ch emical vapor deposition-grown HBTs with a C-doped base after RTP at tempera tures greater than 600 degrees C. Our studies show that high-temperature RT P could induce undesirable degradation in AlGaAs/GaAs HBTs. Different degra dation mechanisms, which are similar to those for the degradation of the Be - and C-doped base HBTs under current-induced stress, are responsible for t he degradation of the Be- and C-doped HBTs subjected to RTP. The degradatio n of Be-doped HBTs is believed to be due to the outdiffusion of Be from the highly doped base, whereas the decrease of current gain for C-doped HBTs i s closely related to the unintentionally incorporated hydrogen during mater ial growth. (C) 1999 American Institute of Physics. [S0021-8979(99)08423-6] .