Organic Ring Oscillators with Sub‐200 ns Stage Delay Based on a Solution‐Processed p‐type Semiconductor Blend. (8th January 2016)

• Record Type: Journal Article
• Authors: Watson, Colin P.; Brown, Beverley A.; Carter, Julian; Morgan, John; Taylor, D. Martin
• Is Part Of: Advanced Electronic Materials. Volume 2:Number 3(2016)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-01-08
• Subjects: inverters -- organic semiconductors -- OTFT model -- p‐type blends -- ring oscillators; Materials -- Electric properties -- Periodicals; Materials science -- Periodicals; Magnetic materials -- Periodicals; Electronic apparatus and appliances -- Periodicals; 537
• DOI: 10.1002/aelm.201500322
• Languages: English
• ISSNs: 2199-160X

Abstract

Abstract : High‐frequency ring oscillators with sub‐microsecond stage delay fabricated from spin‐coated films of a specially formulated small‐molecule/host‐polymer blend are reported. Contacts and interconnects are patterned by photolithography with plasma etching used for creating vias and removing excess material to reduce parasitic effects. The characteristics of transistors with 4.6 μm channel length scale linearly with channel width over the range 60–2160 μm. Model device parameters extracted using Silvaco's Universal Organic Thin Film Transistor (UOTFT) Model yield values of hole mobility increasing from 1.9 to 2.6 cm 2 Vs −1 as gate voltage increased. Simulated and fabricated V gs = 0 inverters predict that the technology is capable of fabricating 5‐stage ring oscillators operating above 100 kHz. Initial designs operated mainly at frequencies in the range 250–300 kHz, due to smaller parasitic gate overlap capacitances and higher supply voltages than assumed in the simulations. A design incorporating graded inverter sizes operates at frequencies above 400 kHz with the best reaching 529 kHz. The corresponding stage delay of 189 ns is the shortest reported to date for a solution‐processed p‐type semiconductor and compares favorably with similar circuits based on evaporated small molecules. Significant further improvements are identified which could lead to the fabrication of digital circuits that operate at much higher bit rates than previously reported. Abstract : The simulation and fabrication of high performance transistors, inverters, and ring oscillators based on an organic p‐type polymer/small molecule blend as the active semiconductor is reported. With carrier mobility approaching 3 cm 2 Vs −1, fabricated 5‐stage ring oscillators operate routinely in the range up to 529 kHz. The corresponding stage delay, 189 ns, is the shortest achieved for a spin‐coated organic semiconductor.