Organic Permeable Base Transistors – Insights and Perspectives

Abstract

Vertical organic transistors have emerged as a new device concept holding great promise to overcome the limitations of lateral organic transistors. In this regard, the organic permeable base transistor (OPBT), a special kind of vertical transistor, stands out due to excellent performance figures such as low‐voltage operation and high transition frequency measured in a pulse‐biasing mode. On the occasion of Prof. Karl Leo's 60th birthday, his contributions to the development of high‐performance OPBTs are honored and a perspective for the future of OPBT development is provided. The current state of the art of OPBTs is reviewed and the principles of the device operation are summarized. New insights into the formation of the permeable base layer, which is vital to the function of OPBTs, are discussed. Additionally, a full yield analysis on a batch of 144 equivalent OPBTs is reported and the device yield and temporal evolution of device parameters are statistically analyzed. This analysis proves a device yield of >90% for these short‐channel transistors, rendering the possibility for circuit integration. Finally, the scaling laws of OPBTs are derived and strategies for new materials and device layouts to push the performance to the gigahertz regime are concluded.

A Critical Outlook for the Pursuit of Lower Contact Resistance in Organic Transistors

“…DPh-DNTT thin-films is exceptionally low in comparison to thin-films of other organic semiconductors, making DPh-DNTT potentially relevant also for vertical transistors, such as OPBTs. [7,47]…”

“…This potentially indicates that the vertical access resistance component from the vacuum‐deposited polycrystalline DPh‐DNTT thin‐films is exceptionally low in comparison to thin‐films of other organic semiconductors, making DPh‐DNTT potentially relevant also for vertical transistors, such as OPBTs. [ 7,47 ]…”

“…Organic semiconductors have been implemented in a variety of electronic devices, including organic light-emitting diodes (OLEDs), [1] organic solar cells, [2] organic photodetectors, [3] and organic transistors of various forms. [4][5][6][7] An essential requirement for all these devices is the efficient injection and/or extraction of charges across the interfaces between the organic semiconductor(s) and the electrical contacts. [8] Extensive research and development efforts into the active materials and the device engineering required for achieving efficient charge injection/ extraction have therefore been instrumental in enabling, for instance, the commercialization of OLEDs.…”

Vertical organic transistors with short channels for multifunctional optoelectronic devices

“…Compared to SBVTs and MISVTs, SCLVTs display the unique advantage of combining low operating voltages and high operating speeds. 59,77–79 By incorporating a SCLVTs and an OLED into a single device, Wu et al demonstrated an OLET with a permeable base emitting the three primary colors. 80 A schematic cross-section of the VOLET structure indicating the material used for each primary color is depicted in Fig.…”

High‐Frequency Operation of Vertical Organic Field‐Effect Transistors

“…Furthermore, the function of the devices crucially relies on the thin, permeable base electrode and its fabrication is still one of the main challenges. [26,27] The second promising concept, the vertical organic field-effect transistor, resembles a lateral transistor in its device. The gate electrode is located underneath the source electrode and not between the source and drain electrodes.…”