Improving characteristics of Si-based trench-electrode metal-semiconductor-metal photodetectors using self-aligned process

A one-mask self-aligned process was used to fabricate trench-electrode (U-grooved) Si-based metal-semiconductor-metal (MSM) photodetectors (PDs). The photo to dark current ratio, responsivity and quantum efficiency of the obtained Si MSM-PD with electrode spacing (S)=5 μm and width (W)=3 μm were 8.65×10³, 0.32 (A/W) and 0.48, respectively, under a 2 V bias voltage. Also, compared with a previously reported similar nonself-aligned device which had a dark current of 6.6 nA, the dark current of the device with a self-aligned electrode could obviously be reduced to 1.4 nA, at 4 V bias voltage. The experimental results also indicated that the responsivity and quantum efficiency of the self-aligned devices could be enhanced from 0.09(A/W), 0.14-0.23 (A/W), 0.34, respectively, under 4 V bias voltage by increasing the active area of the device from 50×50 to 100×100 μm²