Higher Picosecond Photoresponsivity Realized by Introducing Hole-Capturing Levels of Iron in GaAs

Abstract

Control of transient carrier populations has been achieved by the use of carrier-capturing properties of relevant individual deep levels. Slow contribution from holes to transient photocurrents has been successfully suppressed so that the fast component of electron current becomes dominant. This has been realized by introducing deep acceptor levels of iron into undoped semi-insulating GaAs bulk material. Photoresponses to picosecond light pulses with and without iron doping were compared. A sharp peak at the leading edge, whose width is less than 100 ps, is increased for the iron-doped one. An additional cause of this could be reduced electron capture due to a concomitant decrease of deep donors such as electron levels No. 2 (EL2) and No. 6 (EL6). Iron-diffused epitaxial material, which has much lower concentrations of grown-in deep levels, showed the same electron-dominated characteristics, confirming the effectiveness of the hole-capturing nature of the iron level.