Responsivity enhancement of InGaAs based MSM photodetectors using 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/spl times/50 /spl mu/m/sup 2/ area and interdigitated electrodes with 2 /spl mu/m finger-spacing and finger-width exhibit a dark current density less than 10 pA//spl mu/m/sup 2/, 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.