Improved Performance Double Heterostructure InGaP Heterojunction Bipolar Transistors

High frequency systems designers are now employing III-V heterostructure bipolar transistors (HBTs) in low power portable applications as well as in high power systems. Although most devices have used AlGaAs as the wide bandgap emitter, AlGaAs-based devices have had reliability problems at high current densities and high device operation temperatures. Advantages in device performance and fabrication are realized if the AlGaAs emitter is replaced by InGaP. High voltage and high frequency performance of InGaP emitter-based transitors can potentially be further improved by replacing the GaAs collector with InGaP in a double heterostructure provided that band discontinuities between the collector and base can be controlled. In Phase I we propose a novel structure to control the band interface and to fabricate large area double heterostructure InGaP HBTs for comparison with single heterostructure InGaP HBTs. In Phase II we will optimize growth conditions to achieve the optimum band structure at the collector-base junction as defined by improved device results. Wafers will also be sampled to commercial HBT manufacturers and Wright Laboratory and other Government labs for evaluation in RF devices and circuits and will be made commercially available in Phase III.