The Secret Ingredient for Exceptional Contact‐Controlled Transistors

Abstract

Contact‐controlled transistors are rapidly gaining popularity. However, simply using a rectifying source contact often leads to unsatisfactory operation, merely as a thin‐film transistor with low drain current and reduced effective mobility. This may cause otherwise promising experiments to be abandoned. Here, data from literature is analyzed in conjunction with devices that have been recently fabricated in polysilicon, organic and oxide semiconductors, highlighting the main factor in achieving good saturation, namely keeping saturation coefficient γ well below 0.3. Secondary causes of suboptimal electrical characteristics are also discussed. Correct design of these alternative device structures will expedite their adoption for high gain, low‐frequency applications in emerging sensor circuits.

Extraordinarily Weak Temperature Dependence of the Drain Current in Small‐Molecule Schottky‐Contact‐Controlled Transistors through Active‐Layer and Contact Interplay

“…[1] Valuable applications in lighting, [2] biosensing, [3] or security [4][5][6] arise from the versatile processability [7] of these materials, particularly when high-throughput methods, such as roll-to-roll characteristics. However, among several key design criteria, [27] the superior analog performance of SGTs is primarily enabled by the deliberate introduction of a sizeable energy barrier at the source contact, [16,17,28] which is capable of fully depleting the semiconductor at the source edge (Figure 1b,c). Of several avenues into creating energy barriers at the source, [29][30][31] the simplest method would be to implement a Schottky contact.…”

High-Performance Organic Source-Gated Transistors Enabled by the Indium-Tin Oxide–Diketopyrrolopyrrole Polymer Interface

“…Note that while our SGTs with a simple structure and conventional materials achieved remarkably high performance, especially in terms of operating voltage and γ, our maximum A i is not superior to those of several reported organic and inorganic-based TFTs. , It is inferred that a strategic modification of the transistor device geometry may further improve the A i of our system, which can include the use of a lateral field-relief structure. , …”

“…It is the saturation coefficient (γ) corresponding to the ratio between V sat and V G shifts. A recent work pinpointed a theoretical background behind this γ parameter associated with the capacitive voltage divider rule . With C i as the insulator capacitance per unit area and C s as the semiconductor capacitance per unit area, we can write γ = normald V sat normald V normalG = C normali C normali + C normals = k normali t normals k normali t normals + k normals t normali where the last expression is intended as a practical design guideline.…”

“…Because the functioning of SGTs is dominated by the source/channel interface, we chose to cite both the electrode and semiconductor materials. These previously reported organic SGTs incorporated Al/pentacene, Au/N2200, Cu/dinaphtho­[2,3-b:2′,3′- f ]­thieno­[3,2- b ]­thiophene (DNTT), Cr/poly­(indenofluorene-phenanthrene) (PFIPA), and Ag/N2200 interfaces. Figure f shows that the ITO/PDPP4T SGT proposed in this work compares favorably with the reported organic SGTs, featuring a competitively low-voltage high-quality current saturation behavior.…”

“…0.5–0.6 eV) in a staggered TFT structure can trigger the so-called source-gating phenomenon, through which the geometrical source-gate overlap region becomes strongly depleted, and the electrical switching of the entire transistor is governed by the electrostatic modulation in this overlap region. − In other words, an SGT is devised to maximize the contact effects for unconventional functionalities. Although the incorporation of a non-negligible E b is likely to sacrifice several device parameters, such as transconductance ( g m ) and transit frequency of a transistor, the unique contact-controlled mechanism of SGTs is known to offer advantages in terms of output resistance ( r o ), intrinsic gain ( A i ), power consumption, uniformity, and stability. − In this regard, there is a rapidly growing interest in SGTs, which resulted in recent publications on the fundamentals and applications of SGTs covering a wide range of materials, processing, and device architectures. − …”