Influence of bias voltage on the performance of polarization-sensitive near-infrared photodiode based on dilute nitride GaNAs

Recent advances in ultrafast light polarization modulation and electrical control of polarization have increased the demand for polarization-sensitive photodetectors to enable polarization-based optical communication systems. The conduction electron population of dilute nitride GaNAs changes with excitation light polarization owing to the spin-dependent recombination of conduction electrons via the dynamic polarization of defect electron spins. However, polarization-sensitive photodetectors that utilize this property are limited to photoconductive devices with a long response time. In this study, we developed a polarization-sensitive near-infrared photodiode based on GaNAs. The influence of light power and bias voltage on the discrimination efficiency between circularly and linearly polarized light was investigated using coupled rate equation analysis for polarization-dependent photocurrent characteristics. At −2.0 V, where the discrimination efficiency reached 1%, the extraction time of the conduction electrons to the electrode was estimated to be 34 ps. This result suggests that the developed polarization-sensitive photodiode can operate at 10 GHz. The discrimination efficiency increased with light power because of the activated spin-selective capture of conduction electrons by spin-polarized defect states for circularly polarized light, whereas it decreased with increasing reverse bias voltage. This low performance originates from suppressed spin-selective capture, which is due to the combination of electric-field-induced spin relaxation and a decrease in the capture efficiency of conduction electrons. This study provides valuable insights into the influence of the bias voltage on the polarization-dependent photocurrent, which is a key challenge to the realization of practical polarization-sensitive photodiodes based on the spin-dependent recombination effect of conduction electrons.