Ultra-Low Power Stress Sensing By Leakage Current of P-N Junctions

Ultra-low power sensors attract increasing attention as the requisite building blocks of long-life wireless sensor nodes. This work developed a proof-of-concept device to evaluate the feasibility of ultra-low power stress sensing by the leakage current of p-n junctions. Experimental results show that the variation of the leakage current of p-n junctions demonstrates excellent linearity and stability with the stress in the range from 0 to 90 MPa. When the reverse bias voltage decreases from 2.5 to 0.5 V, there is almost no deterioration of the stress sensitivity but the maximum power consumption greatly decreases from to 705 pW to 156 pW. By using the published circuit for temperature sensors, the power consumption of the stress/strain sensors based on the detection of the leakage current of p-n junctions may be decreased to lower than 1 nW. Therefore, the piezojunction effect of p-n junctions is an attractive sensing mechanism for ultra-low power stress/strain sensors.

I. Introduction

In recent years, billions of energy-autonomous wireless sensor nodes are being mounted to collect information for home automation, building monitoring and environmental monitoring [1]-[3]. For example, if the early damage of long-span bridges or dams is not detected and continues to develop and accumulate to a certain extent, the entire structure may suffer a sudden failure, which is a disaster to people’s lives and property [4]. Therefore, using the wireless sensor nodes to monitor the health status is of significance to extend the lifetime and ensure the safety of infrastructures. In these cases, the wireless sensor nodes are required to work for many years without any maintenance, setting a drastic requirement on the power sources and the power consumption [1], [2]. On the one hand, batteries with higher energy density and miniatrized energy harvesters, which convert ambient solar energy, vibration energy and wind energy into electricity, have been developed as the power sources of these nodes [5]-[9]. On the other hand, ultra-low power sensors based on new mechanisms attract increasing attention [3], [9].