High photoconductive gain in a GaAs/PbS heterojunction based SWIR detector

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An internal quantum efficiency (IQE), defined as the electron-hole pair to photon conversion ratio, of ∼10 was obtained for an n-GaAs/p-PbS heterojunction when illuminating the device with short wavelength infrared (SWIR) light in the wavelength range of 1300 nm-1500 nm. The PbS layer, which was comprised of nano-scale domains (NDs) grown by Chemical Bath Deposition (CBD), was quantum confined to absorb SWIR light. The heterojunction showed tunneling characteristics with a soft breakdown at a relatively low reverse bias (∼-1 V) and a strong photoconductive response at a negative bias above -1.8 V. The voltage dependent behavior is explained using the band structure of the heterojunction. The high IQE observed in the photoconductive response at -2 V is attributed to a high photoconductive gain of more than 40. This assumption was confirmed by mixed conduction behavior observed in a magnetic field dependence Hall effect measurement. These measurements enabled extracting concentrations and mobilities of both electrons and holes. It was found that the CBD grown p-type PbS NDs layer has a mixed conduction nature due to the high electron-to-hole mobility ratio of more than one order of magnitude. This explains the high photoconductive gain achieved and, thus, the high IQE measured for these devices.

Original languageEnglish
Article number081107
JournalApplied Physics Letters
Issue number8
StatePublished - 24 Aug 2020

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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