Electrical and thermal characteristics of heterojunction bipolar transistors fabricated on peeled film epitaxial layers

The feasibility of peeling the active AlGaAs/GaAs heterojunction bipolar transistor (HBT) epitaxial thin films from the original GaAs substrate and the subsequent van der Waals bonding of the films to AlN, InP and diamond on silicon substrates is discussed. HBTs were first fabricated on epitaxial layers containing an AlAs separating layer. The wafer was divided, and a portion of the wafer was then peeled and van der Waals bonded to various substrates. The van der Waals bond demonstrated excellent thermal and mechanical stability by withstanding subsequent processing steps up to 250°C. The lifted devices bonded to the higher thermal conductivity substrates show excellent DC and RF performance. The average device junction temperature was also characterized. Further improvements can be accomplished by utilizing substrates with a smooth surface morphology having a high thermal conductivity