High speed InGaP emitter HBTs fabricated with ECR dry etch technique

The rapid progress of epitaxial growth of InGaP/GaAs heterostructures and the device results of tunneling emitter and heterojunction bipolar transistors (TEBTs and HBTs) using InGaP have raised much interest in pursuing their high speed applications. The small conduction band discontinuity and excellent interface quality of the InGaP/GaAs HBT provides a much smaller offset voltage and relatively high current gain at low current density, as compared to the conventional AlGaAs/GaAs HBTs. Superior performance of low frequency noise, low base sheet resistance, and etching selectivity of InGaP over GaAs, were also addressed. Although promising results of microwave small signal and power performance of InGaP/GaAs HBTs were demonstrated, overall performance superior to the AlGaAs emitter HBTs is yet to be accomplished. This can be achieved through the optimization of layer structures and the dry etch technology for device fabrication since device technologists have not explored the full potential of this heterojunction. In this paper, we will discuss our etching approach and device results on this subject; but the emphasis is on microwave power application