n-AlGaAs/p-GaAs/n-GaN HETEROJUNCTION BIPOLAR TRANSISTOR: THE FIRST TRANSISTOR FORMED VIA WAFER FUSION

We discuss the first reported device characteristics of a wafer-fused heterojunction bipolar transistor (HBT), demonstrating the potential of wafer fusion for the production of electrically active heterostructures between lattice-mismatched materials. n-GaAs/n-GaN (“n-n”) and p-GaAs/n-GaN (“p-n”) heterojunctions were successfully fused and processed into current-voltage (I-V) test structures. The fusion and characterization of these simple structures provided insight for the fabrication of the more complicated HBT structures. Initial HBT devices performed with promising dc common-emitter I-V characteristics and Gummel plots. n-n, p-n, and HBT electrical performance was correlated with systematically varied fusion conditions, and with the quality of the fused interface, given both chemical information provided by secondary ion mass spectroscopy (SIMS) and structural information from high resolution transmission electron microscopy (HRTEM) analysis.