Schottky‐Barrier‐Controllable Graphene Electrode to Boost Rectification in Organic Vertical P–N Junction Photodiodes

Abstract

Monolayer graphene is used as an electrode to develop novel electronic device architectures that exploit the unique, atomically thin structure of the material with a low density of states at its charge neutrality point. For example, a single semiconductor layer stacked onto graphene can provide a semiconductor-electrode junction with a tunable injection barrier, which is the basis for a primitive transistor architecture known as the Schottky barrier field-effect transistor. This work demonstrates the next level of complexity in a vertical graphene-semiconductor architecture. Specifically, an organic vertical p-n junction (p-type pentacene/n-type N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C 8 )) on top of a graphene electrode constituting a novel gate-tunable photodiode device structure is fabricated. The model device confirms that controlling the Schottky barrier height at the pentacene-graphene junction can (i) suppress the dark current density and (ii) enhance the photocurrent of the device, both of which are critical to improve the performance of a photodiode.

Reverse dark current in organic photodetectors and the major role of traps as source of noise

“…Dark current suppression in organic diodes has been the subject of several reports in the literature 3 . Most frequently used approaches are charge selective layers 4 , 5 , contact alignment 6 , 7 , prevention of shunt paths via layer thickness increase 8 , and interlayers to smoothen the bottom contact 9 , 10 , as well as charge transport layer structuring 11 . While the above-mentioned J D suppression approaches lead to an improved OPD performance, a comprehensive understanding of the intrinsic and extrinsic sources of dark current is still missing, which would provide insights for future device optimization using improved materials or architectures.…”

2D–Organic Hybrid Heterostructures for Optoelectronic Applications

“…After study of the basic charge transport properties as discussed above, a series of organic materials such as DNTT, pentacene, C 60 , N , N ′‐dioctyl‐3,4,9,10‐perylenedicarboximide (PTCDI‐C8), C8‐BTBT, covalent organic frameworks, P3HT, pentacene/PTCDI‐C8, and pentacene/C8‐BTBT heterostructures were studied by preparation of heterostructures on graphene or reduced graphene oxide (rGO) . The high operating voltage of a graphene/organic barristor with a SiO 2 gate dielectric can be minimized to less than 5 V by the use of high‐ k dielectrics such as hafnium or aluminum oxides and ion‐gel dielectrics.…”

“…A type‐II heterojunction is formed owing to alignment of the energy bands of the PTCDA and pentacene layers; consequently, numerous electron–hole pairs are generated and effectively separated under the influence of a built‐in electric field upon illumination. This, in turn, promotes charge transfer at the PTCDA/graphene interfaces …”

“…In addition, vertical barristors and floating‐gate transistors with 2D–organic hybrid structures are deemed as unique transistor architectures for PDs . For example, photosensitive barristors based on monolayer graphene interfacing with pentacene/PTCDI‐C8 and PTCDA/C8‐BTBT have been studied . Such devices yield a high I ph / I dark ratio under gate voltage modulation, which cannot be achieved in normal graphene–organic phototransistors.…”

Graphene-based vertical thin film transistors

“…With single atomic thickness, finite density of states (DOS) and weak screening effect, graphene exhibits a field-tunable work-function and partial electrostatic transparency [26,42,[59][60][61][62][63][64][65][66]. It can therefore function as an 'active' contact in tunable graphene-semiconductor or graphene-insulator junction to enable entirely new possibilities for VFET application [42,60,61,[67][68][69][70][71][72][73][74][75].…”