Current gain control of near infrared c-Si phototransistors

Abstract

c-Si phototransistors with base junction depth around 4.0 μm with its common emitter DC current gain h FE within 300–1100 had been well controlled by implanting base doping levels from 3×10 14 to 6×10 14 cm −2, which is suitable in any conventional commercial photosensing application. According to the experimental results, the higher the base doses implanted, the lower and more stable is the DC current gain h FE obtained. The higher base implanting doping level results in reproducible and uniform wafers. The common emitter open base breakdown voltage BV CEO ranges from 35 V (for lightly doped base) to 140 V (for heavier doped base) under the test condition of I CEO=100 μA, and the collector–emitter leakage current for base current I B=0. The open emitter breakdown voltage is within 40 V for lightly doped base, ∼220 V for heavier doped base under I CBO=100 μA and I E=0 A. The breakdown mechanism includes punch through and avalanche multiplication.