Probing bias and power dependency of high-performance broadband Mg/ZnSnP2/Sn back-to-back Schottky junction photodetectors

Abstract

Two non-identical Mg/ZnSnP2 and ZnSnP2/Sn Schottky diodes connected in coplanar back-to-back configuration are fabricated on p-type silicon (100) substrate for photodetection in the UV-VIS-NIR spectral region. A detailed study of the power and bias dependent responsivity, detectivity, and response and recovery speed of the devices is reported. The responsivity and detectivity were found to be 0.2 A W-1 and 4.62 × 1012 Jones for the Mg/ZnSnP2 and 0.03 A W-1 and 1.62 × 1011 Jones for the Sn/ZnSnP2 junctions, respectively when they were operated without bias. However, under a reverse bias of 2.5 V, these values changed to 4.7 A W-1 and 1.19 × 1012 Jones in the case of Mg/ZnSnP2 and 12.7 A W-1 and 4.78 × 1011 Jones for Sn/ZnSnP2 junctions, respectively. The photocurrents associated with both the junctions were increased superlinearly with illumination power which is correlated to the conversion of the existing traps within the forbidden energy gap to the recombination centers. The response and recovery speed of the photodetectors were also studied under variable bias and illumination power. Under an incident power of 0.34 mW, the rise and decay times for the Mg/ZnSnP2 and Sn/ZnSnP2 junctions were 200 μs, 2300 μs and 390 μs, 240 μs, respectively at 2.5 V. The Mg/ZnSnP2 showed an anomalous bias dependent secondary decay channel which disappeared at self-powered configuration. The frequency-dependent capacitance in the dark and illumination power-dependent capacitance of the structure were also performed to understand the presence of defect states and the capture of photogenerated carriers by the traps and recombination centers.