Improved performance of large-area InP/InGaAs metal-semiconductor-metal photodetectors by sulfur passivation

We report on sulfur based surface passivation technique for InGaAs metal-semiconductor-metal (MSM) photodetectors with an InP barrier enhancement layer. We show that excessive leakage current and photocurrent gain, which are the two major performance-limiting factors in MSM detectors, can be largely suppressed by a treatment of the InP surface with ammonium polysulfide. The dark current and photocurrent characteristics of such passivated devices were monitored over a period of half a year and were found to be stable. The improved performance of the device characteristics is explained in terms of a passivation-induced reduction of surface charging effects.