The impact-ionization-induced avalanche multiplication effect and Early effect in the selectively implanted collector (SIC) bipolar junction transistors are investigated in this paper. The multiplication factor M - 1 and the Early effect factor E - 1 are characterized by a proposed novel technique capable of separating those two contributions to the increment of collector current with collector-base bias of the transistors with and without SIC technology. The collector-base threshold voltage of multiplication factor M - 1 = 10(-5) is shifted from 5 V to below 1 V and the voltage of the Early effect factor E - 1 = 10(-1) is shifted from 5.2 to 2.2 V by the SIC technology with dose of 4 x 10(12) cm(-1) and energy of 360 keV phosphorus implantation.