PROJECT TITLE :
Effects of Electrical Stress on the InGaP/GaAs Heterojunction Phototransistor
Though the effects of electrical stress on the performance of InGaP/GaAs heterojunction bipolar transistors (HBTs) have been widely studied and reported, few or no reports on the InGaP/GaAs heterojunction phototransistors (HPTs) have been revealed. During this paper, we discuss the phototransistor characteristics before and when the electrical stress applied at room temperature and at hot temperature, and assess the effectiveness of the emitter-ledge passivation, which was found to stay the InGaP/GaAs HBTs from degrading at higher temperature or due to electrical stress. A area-temperature electrical stress was applied to the HPTs by maintaining a current density of thirty seven A/cm2 for one h at room temperature. The electrical stress was lower by two to 3 orders than the stress typically applied to the HBTs for the strain study and failed to cause vital decreases in the space-temperature current gain and photoresponse, but it significantly degraded the characteristics of the InGaP/GaAs HPTs at 420 K. In order to accelerate the degradation, the high-temperature stress was applied to each HPTs with and while not the emitter-ledge passivation at 420 K. Though the present density was the identical and the stress time was reduced to fifteen min, the high-temperature stress considerably decreased the current gain and collector photocurrent of the HPT without the emitter-ledge passivation over the entire measurement temperature vary of three hundred–420 K. The emitter-ledge passivation suppresses the recombination via defects at the emitter perimeter and is found to be more effective than that in the HBTs.
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