An InGaP/GaAs HBT/JFET BiFET technology for PA bias circuit applications

Brian Moser, W. Wohlmuth, S. Nedeljkovic, W. Clausen, D. Halchin, R. Vass, and M. Fresina
RFMD, 7628 Thorndike Rd. Greensboro, NC 27409-9421
Email: bmoser@rfmd.com, Phone: (336) 931-8573

Keywords: InGaP, HBT, JFET, BiFET, integration, VVR

Abstract
This BiFET technology integrates a JFET device, also called a voltage-variable resistor (VVR) device, into the emitter layer structure of an InGaP/GaAs HBT. This new VVR device enables new PA bias circuit designs with lower or no voltage reference. This technology only requires one additional mask, one additional etch, and 2 additional epi layers as compared to an HBT-only process. These minimal changes add minimal cost to this BiFET process. The HBT device showed no appreciable performance trade-offs with the additional epi layers. Since the p-n heterojunction controls the drain current rather than a gate metal, manufacturing this device requires tight control of the InGaP emitter, GaAs channel, and InGaP etch stop layers. Doping and thickness control both across-wafer and wafer-to-wafer are needed to make the VVR a repeatable and manufacturable device.
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