ANALYSIS OF THE DEVICE-SIZE DEPENDENCE OF THE CURRENT GAIN IN GAINP GAAS HBTS/

The effect of the emitter area on the current-voltage characteristics of GaInP/GaAs heterojunction bipolar transistors (HBTs) has been studi ed. In this research, the advantages of employing GaInP as a wide-band gap emitter for small-sized HBTs, compared to AlGaAs, will be presente d experimentally. It is demonstrated that GaInP/GaAs HBTs show an incr easing current gain as the device size becomes smaller, while AlGaAs/G aAs HBTs show the well-known emitter-size effect of the current gain. From the Gummel plots, the current components contributing to the vari ations of the common emitter current gain with the device size are ana lyzed in detail. We present a modified terminal current expression bas ed on the Gummel-Poon static model and analyze the device size depende nce of the 1-kT and 2-kT current components. It is found that the vari ation of the current gain in various dimensional devices is dependent on the 1-kT current component.