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- In this paper, Heterojunction phototransistors(HPT's) with an optically transparent ITO emitter contacts were fabricated. The ITO ohmic contacts were realized by employing thin indium layer between the ITO and n+-InP layers. The ITO contact was annealed at 250oC. The specific contact resistance of about 6.6×10-4Ω㎠ was measured by use of the transmission line model (TLM). Heterojunction bipolar transistors (HBTs) having the same device layout were fabricated to compare with HPTs. The DC characteristics of the InP/InGaAs HPT showed the similar electrical characteristics of the HBT. Emitter contact resistance(RE) of about 6.4Ω was extracted , which was very similar to that of the HBT. The optical characteristics of HPT's were generated by illuminating the device with light from 1.3㎛ light. It showed that HPT's can be controlled optically.