Abstract
Abstract In this work, we first review the bandgap theory of the SiGe Heterojunction Bipolar Transistor (HBT), and it's current vs. voltage characteristics. Because the base region bandgap is smaller than that of collector region, so, it has bandgap discontinuity nearthe base-collectorjunction. From the Schrodinger Equation, it can be derivedthat two discrete quantum energy levels exist in theconduction band discontinuity. When the emitter-base junction is forward biased by a voltage Vbe on the normal working region, then sweep the base-collector reverse biased voltage Vcb, We can find current jumps in the figure of IC vs. Vcb and IB vs. Vcb. This is because the electron in the discrete quantum energy level will penetrate to thedepletion region of the collector, then enlarged by themultiplication effect. This effect is analyzed under different emitter-base forward bias voltage Vbe,and under different temperatures.