Study on the Off-State Breakdown Mechanism and Performance of Copolymer Lateral Drift Region-Organic Field-Effect Transistor Using TCAD Tool

The outstanding off-state breakdown performance of lateral drift region organic field-effect transistors (LDR-OFETs) has uncovered the capability of copolymer organic semiconductors (OSCs) in sustaining high voltage. Yet, the breakdown mechanism and performance of LDR-OFET remain unexplored due to the missing mature theories and analytical models. In this article, through the combination of commercial technology computer-aided design (TCAD) tools and fabricated copolymer OSC-based lateral power devices, the avalanche-like breakdown mechanism and impact ionization process are theoretically verified in copolymer OSCs. The fabricated OFET and LDR-OFET feature a poly(methyl methacrylate) (PMMA) and a diketopyrrolopyrrole-based conjugated copolymer (DPPT-TT) thin film as the gate insulator layer and semiconductor layer, respectively. According to the simulations, the equivalent p-n junction and p-i-n junction are formed as the reverse-biased voltage is applied on conventional OFET and LDR-OFET, respectively. The off-state breakdown performance of OFET is therefore determined by the parallel structure of p-n/p-i-n junction and Schottky junction. Both the Schottky contacts and the equivalent p-n/p-i-n junction contribute to the avalanche-like breakdown, yet for the LDR-OFET, the equivalent p-i-n junction takes most part of the applied voltage, guaranteeing it possesses an improved off-state breakdown performance. The good agreement between the simulated and measured results verifies the correctness of the proposed simulation methodology, providing an effective simulation approach for further analysis of copolymer OSC-based lateral power devices.