Premium
Organic Ring Oscillators with Sub‐200 ns Stage Delay Based on a Solution‐Processed p‐type Semiconductor Blend
Author(s) -
Watson Colin P.,
Brown Beverley A.,
Carter Julian,
Morgan John,
Taylor D. Martin
Publication year - 2016
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201500322
Subject(s) - materials science , ring oscillator , photolithography , optoelectronics , transistor , electronic circuit , inverter , thin film transistor , fabrication , microsecond , voltage , nanotechnology , electrical engineering , cmos , layer (electronics) , optics , medicine , alternative medicine , pathology , engineering , physics
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.