Millimeter-wave AlGaAs-GaAs HBT power operation

Abstract
The AlGaAs-GaAs HBT has demonstrated good power performance up to 18 GHz. Although f/sub max/ is typically above 100 GHz, the power performance limitation and large signal operation at millimeter wave frequencies have not been studied. Power results from two HBT structures at 35 GHz are analyzed based on numerical simulation. The HBT demonstrated 8.5-dB linear power gain, 30% PAE with 7.8-dB gain and 7.5-V V/sub ce/ bias. The power density reaches 1.25 mW/ mu m/sup 2/. A shorter collector (0.4 mu m) is shown to be better suited for 35-GHz operation as a result of shorter collector transit time and smaller residual collector voltage. Improvement can be achieved by reducing the base and collector resistance, and the collector capacitance.

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