Deep-level transient spectroscopy (DLTS) measurements have been performed on SiGe heterojunction bipolar transistors fabricated in a complementary metal-oxide-semiconductor compatible polysilicon self-aligned process. A detailed study of the emitter-base capacitance transient as a function of the filling pulse parameters and transistor geometry has shown that the deep levels are correlated to point defects uniformly distributed along the emitter-base junction periphery and attributed to the reactive ion etching (RIE) process. The observed deep electron traps are located at 0.6 eV below the conduction band with a capture cross section of 10(-17) cm(2). In order to confirm that the observed defects were not correlated to the SiGe base material, a similar investigation was carried out on mesa devices grown in the same reactor with the same intrinsic structure but whose emitter-base active zone did not suffer RIE. In these devices, a new electron trap with an activation energy of 0.38 eV and a capture cross section of 10(-19) cm(2) is detected. This trap is sensitive to the electric field as in the case of the self-aligned structure, but a detailed study has shown that it has a different origin. Finally, the first peripheral electron trap at E-c -0.6 eV is not observed in mesa devices in good agreement with our first hypothesis.