Responsivity enhancement of InGaAs based MSM photodetectorsusing 2DEG layer sequence and semitransparent electrodes

The optoelectronic behaviour of InGaAs based metal-semiconductor-metal photodetectors with semitransparent electrodes is investigated. The devices with 50 × 50 µm2 area and interdigitated electrodes with 2 µm finger-spacing and finger-width exhibit a dark current density less than 10 pA/µm2, a breakdown voltage of 45 V and a saturation capacitance of 30 fF. A DC responsivity of 0.61 A/W and a –3 dB bandwidth of 8.5 GHz were achieved. The electric potential distribution is modified by a 2DEG inserted in the layer structure leading, to improved bandwidth.