High power GaAlAs/GaAs HBTs for microwave applications

Abstract

This paper reports the attainment of high microwave output, up to 0.4 W cw at 10 GHz, with GaAlAs/ GaAs heterojunction bipolar transistors. In addition to high power, the HBTs displayed excellent power-added efficiency (4896) and power gain (7 dB). A key factor in obtaining these high powers and efficiencies is the ability to support high collector-emitter voltages without breakdown. Breakdown voltage was up to 23 V (BV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cbo</inf> ) in the devices reported here. The experimental data are in good agreement with a theoretical model of I-V characteristics near breakdown. The cutoff frequency f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</inf> was found to vary with V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</inf> as expected for electron-drift at a saturation veloclty of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> cm/s across the base-collector depletion region.