摘要：The effects of the composite-collector structure and the δ-doping density in InGaAs/InP DHBT on the Kirk current have been *** effective grade layer in the discretely graded layer goes into the InGaAs setback *** formulas of the maximum doping density,the maximum Kirk current,and the corresponding δ-doping density are derived under different Kirk-effect *** the maximum collector doping density and the maximum Kirk current are dependent on the δ-doping *** opti-mizing the delta doping,the Kirk current density can be greatly increased.