Fast InGaAs photoconductive detectors with speed enhanced by Berylium ion bombardment

An InGaAs photoconductive detector which exhibits the gain mechanism of an n-type photoconductor as well as the subnanosecond response time characteristic of radiation damaged photoconductors is presented. We show how the free carrier lifetime and mobility as well as the dark resistivity depend on the Be ion radiation dose for both undoped and Fe doped InGaAs. Greater than unity photoconductive gain is demonstrated for large size (15 micron electrode spacing) devices with a 1/e response time of 400 ps. The speed of response of the irradiated photoconductors degrades at low illumination levels due to the presence of saturable traps with nanosecond emission times. We attribute these traps to surface states intrinsic to InGaAs.