Hafnium oxide passivation of InGaAs/InP heterostructure bipolar transistors by electron beam evaporation

In this contribution, we investigate the passivation of InGaAs/InP heterostructures using plasma assisted e-beam evaporated hafnium oxide (HfO 2). The microstructure and optical properties of the HfO 2 layers are first examined by X-ray reflectivity and spectroscopic ellipsometry on Si substrates. The current gain and breakdown voltage of InGaAs/InP heterostructure bipolar transistors (HBTs) have subsequently been used to evaluate the impact and efficiency of the e-beam evaporated HfO 2 passivation layers. The results from these structures have been contrasted with data from similar samples encapsulated with SiO 2 using conventional plasma enhanced chemical vapor deposition. The HfO 2 passivated InGaAs/InP HBTs show comparable current gains as compared to unpassivated structures. More importantly, in contrast to SiO 2-PECVD devices, the common emitter characteristics of HfO 2 passivated HBTs show no degradation in device breakdown voltage.