New Structural Design of Gated Lateral Bipolar Junction Transistor for Sensor Applications

In this paper, we propose a gated lateral bipolar junction transistor (GLBJT) that has a cascade structure, resulting in improved sensing performance over conventional GLBJTs. The device can be operated in bipolar junction transistor (BJT) mode, metal-oxide-semiconductor field-effect transistor (MOSFET) mode, and a hybrid MOSFET-BJT mode under input bias control. The device exhibits higher transconductance than that of conventional GLBJTs owing to the cascade structure using pMOSFET. The cascade effect generated in the proposed device is shown to increase the transconductance, and the results from two experiments [pH response and C-reactive protein (CRP)-antigen detection] demonstrate that the sensitivity of the proposed sensor exceeds that of conventional GLBJTs. The proposed device offers approximately 2.5 times that the sensitivity of conventional GLBJTs in the pH and CRP-antigen detection experiments. These results confirm that the proposed device has enhanced sensitivity and suggests the possibility of realizing more efficient sensors with better sensitivity than that of conventional GLBJTs.