Permeable Base Transistor Research Articles

Stable room temperature magnetocurrent in electrodeposited permeable n-type metal base transistor

We investigated a permeable metal base transistor consisting of a ZnO/NiFe/Si heterostructure. Both ZnO and NiFe layers were grown by electrodeposition techniques, using only adhesive tape masks to define deposition regions. The base permeability can thus be controlled by varying the NiFe deposition time. We report here our best results obtained for the permeable NiFe base close to the electrical percolation threshold, which gives reasonable sensitivity to the device. Magnetocurrent measurements carried out at room temperature show that this permeable metal base transistor is stable and sensitive under applied magnetic fields of low intensities, ∼100 Oe, required for electronics integration.

Modeling of Organic Permeable Base Transistor Based on Inverse of Transistor Efficiency ( ${I}_{C}$ / ${g}_{m}$ )

For the first time, we are proposing characteristic equation, which describes the behavior of an organic permeable base transistor (OPBT). For this, an OPBT has been fabricated and studied through the experimentally obtained ${I}_{C}$ / ${g}_{m}$ versus ${V}_{\mathsf {BE}}$ (base-emitter voltage) characteristics. The characteristic equation, i.e., collector current, ${I}_{C} = {k}$ ( ${V}_{\mathsf {BE}} - {V}_{\mathsf {th}})^{n}$ has been obtained through curve fitting and mathematical formulations. Six OPBTs (modified by inserting a layer of barrier material of either N, $\text{N}^{\prime }$ [(-di-[( $\alpha$ -naphthyl)-N, $\text{N}^{\prime }$ -diphenyl]-1, $1^{\prime }$ -biphenyl)-4, $4^{\prime }$ -diamine ( $\alpha$ -NPD) or N, $\text{N}^{\prime }$ -Bis(naphthalen-1-yl)-N, $\text{N}^{\prime }$ -bis(phenyl)-2,7-diamino-9, 9-(Spiro-NPB) between emitter and base layers) confirm that their transfer characteristics follow this equation with n varying between 1.1 and 2.2. The n has been found to be dependent on barrier material. The gain of the device is ${A}_{O} = \textit {nV}_{E}$ / ${V}_{\mathsf {BE}}$ , ${V}_{E}$ being the early voltage.

Organic Power Electronics: Transistor Operation in the kA/cm2 Regime

In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm−2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm2 V−1 s−1, this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed.

Low voltage organic permeable base N-type transistor

A vertical n-type organic permeable metal base transistor was fabricated using N,N-ditridecylperylene-3,4,9,10-tetracarboxylic diimide as an active material for making emitter and collector regions. A composite of Al//C60/Al/AlOx forms the base region of the proposed structure. The detailed study of the Early effect was carried out for determining the intrinsic gain, transconductance, and output impedance which were found to be 92, 145 μΩ−1, and 0.634 MΩ, respectively, at an applied bias of 1 V between collector–emitter contacts. The device is capable of operating at a low voltage of 1 V, which makes it suitable for low voltage and high frequency applications.

Operation mechanism of high performance organic permeable base transistors with an insulated and perforated base electrode

The organic permeable base transistor is a vertical transistor architecture that enables high performance while maintaining a simple low-resolution fabrication. It has been argued that the charge transport through the nano-sized openings of the central base electrode limits the performance. Here, we demonstrate by using 3D drift-diffusion simulations that this is not the case in the relevant operation range. At low current densities, the applied base potential controls the number of charges that can pass through an opening and the opening is the current limiting factor. However, at higher current densities, charges accumulate within the openings and in front of the base insulation, allowing for an efficient lateral transport of charges towards the next opening. The on-state in the current-voltage characteristics reaches the maximum possible current given by space charge limited current transport through the intrinsic semiconductor layers. Thus, even a small effective area of the openings can drive huge current densities, and further device optimization has to focus on reducing the intrinsic layer thickness to a minimum.

Advanced Organic Permeable-Base Transistor with Superior Performance.

An optimized vertical organic permeable-base transistor (OPBT) competing with the best organic field-effect transistors in performance, while employing low-cost fabrication techniques, is presented. The OPBT stands out by its excellent power efficiency at the highest frequencies.

Controlling morphology: A vertical organic transistor with a self-structured permeable base using the bottom electrode as seed layer

Flexible organic permeable base transistors are a promising transistor technology, enabling high transconductance without the need for cost-intensive structuring techniques. Here, we present a simple approach to enhance the transmission and thus the current gain of a permeable base transistor. By adding a morphology modifying gold layer beneath the organic semiconductor, the interface to the base electrode is adjusted, resulting in a self-structured permeable base. Furthermore, we show that doping is essential not only for charge injection at the emitter, but is also required at the collector for a good performance. We show that the transmission can be increased to 98% by tuning the built-in field at the collector to actively gather charge carriers. The built-in field also leads to a very low minimum operation voltage <0.5 V, resulting in a low power consumption.

Intrinsic delay of permeable base transistor

Permeable base transistors (PBTs) fabricated by vacuum deposition or solution process have the advantages of easy fabrication and low power operation and are a promising device structure for flexible electronics. Intrinsic delay of PBT, which characterizes the speed of the transistor, is investigated by solving the three-dimensional Poisson equation and drift-diffusion equation self-consistently using finite element method. Decreasing the emitter thickness lowers the intrinsic delay by improving on-current, and a thinner base is also preferred for low intrinsic delay because of fewer carriers in the base region at off-state. The intrinsic delay exponentially decreases as the emitter contact Schottky barrier height decreases, and it linearly depends on the carrier mobility. With an optimized emitter contact barrier height and device geometry, a sub-nano-second intrinsic delay can be achieved with a carrier mobility of ∼10 cm2/V/s obtainable in solution processed indium gallium zinc oxide, which indicates the potential of solution processed PBTs for GHz operations.

All solution-processed inorganic/organic hybrid permeable metal-base transistor.

All solution-processed inorganic/organic hybrid permeable-base transistor (PMBT) based on nickel oxide emitter and P3HT collector is developed. Due to the high charge injection properties of nickel oxide and spontaneously formed nano-pinholes in the base electrode, the devices exhibit high common-base and common-emitter current gains up to 0.98 and 304, respectively with saturated output current.

Performance of hybrid p-type vertical transistors with poly(N-vinylcarbazole) as emitter and the transfer mechanism of charge carriers through the base

We report hybrid vertical architecture p-type transistors with poly(N-vinylcarbazole) as the emitter, p-type silicon as the collector and Al:Ca alloy layer as the base. The investigation of the common-base and common-emitter characteristics clearly demonstrates that the devices operate as permeable-base transistors (PBTs). The PBTs show common-base current gain α of 0.98 at −VBC = 1.5 V and common-emitter gain β of over 100. Atomic force microscope images of the base layer show an uneven surface, showing that the annealing does not dissolve the charge trap states but offers ‘pinholes’ for the oxidation in-depth even through the whole base layer. In this case, the charge carriers must tunnel the thin oxidized layer, and then are collected. It is clearly seen that there exists a barrier against holes injection from the base to the collector semiconductor at the interface, and the further oxidation caused by exposing the devices in air changes the operational mode of the resulting devices from the PBT to the metal-base transistor.

Fabrication and characteristics of permeable-base organic transistors based on co-evaporated pentacene:Al base

In this letter, fabrication and characteristics of a p-type permeable-base organic transistor are reported. A hole-type organic semiconductor pentacene is used as emitter and collector. The permeable pentacene:Al base is formed by co-evaporating pentacene and Al in vacuum. The device performance has shown to depend on the evaporation rate of pentacene in the pentacene:Al co-evaporation, where the evaporation rate of Al is controlled at 1 nm/s. Controlling the evaporation rate of pentacene at 0.1 nm/s in the pentacene:Al co-evaporation, the device shows the optimal common-base current gain of near 1 and common-emitter current gain of ∼137.

High Mobility Compound Semiconductor Permeable Base Transistors with Suppressed Base Current

Two novel Permeable Base Transistor (PBT) structures for base leakage suppression with lattice-matched In0.53Ga0.47As channel have been proposed. The operations of these novel devices have been analyzed, and their DC and RF performance have been evaluated against the conventional PBT.

High Mobility III-V Permeable Base Transistors with Suppressed Base Current

not Available.

Hybrid Vertical Architecture Transistor with 2,6-Diphenylindenofluorene Based Emitter and Base Permeability Controlled by Polystyrene Spheres Lithography

We report on vertical architecture hybrid transistor devices using p-type silicon as collector terminal and 2,6-diphenylindenofluorene as organic semiconductor in the emitter layer. Polystyrene spheres were used as shadow masks in order to control the diameter and density of the openings in the Al metallic base. Two processes of sphere deposition were used: electrospray and dip-coating. The electrospray deposition leads to a smaller density of sphere agglomerates, but for the used sphere diameter, approximately 200 nm, the transistor performance is similar for devices prepared with sphere deposition by both techniques. The so constructed permeable-base transistors show common-emitter current gain of the order of 10(2).

Hybrid vertical architecture transistor with magnetic-field-dependent current amplification as organic magnetocurrent investigation tool

We prepare hybrid vertical architecture transistors that show magnetic-field-dependent electrical characteristics using tris-(8-hydroxyquinoline) aluminum (Alq3), sulfonated polyaniline (SPAN), and n-type silicon. These transistors have n-type silicon as collector, a 200 nm thick SPAN layer as the base, and an emitter composed by Al/Ca/Alq3(60 nm) layers, showing permeable-base transistor characteristics. The emitter shows very high magnetocurrent when the Al/Ca is negatively polarized with respect to the SPAN, which is the condition of forward active operation mode. The rate of electrons that cross emitter and base layers and reach the collector is affected by the magnetic field, leading to magnetic-field-dependent common-emitter current gain larger than 1. We also demonstrate that the magnetocurrent is due to the contribution of electrons.

Vertical structure permeable-base hybrid transistors based on multilayered metal base for stable electrical characteristics

In this work we present a permeable-base transistor consisting of a 60 nm thick N, N′-diphenyl- N, N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine layer or a 40 nm thick 2,6-diphenyl-indenofluorene layer as the emitter, a Ca/Al/Ca multilayer as the metal base, and p-Si as collector. In the base, the Ca layers are 5 nm thick and the Al layer was varied between 10 and 40 nm, the best results obtained with a 20 nm thick layer. The devices present common-base current gain with both organic layer and silicon acting as emitter, but there is only observable common-emitter current gain when the organic semiconductor acts as emitter. The obtained common-emitter current gain, ∼2, is independent on collector-emitter voltage, base current and organic emitter in a reasonable wide interval. Air exposure or annealing of the base is necessary to achieve these characteristics, indicating that an oxide layer is beneficial to proper device operation.

Vertical structure p-type permeable metal-base organic transistors based on N,N′-diphentyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine

In this article, vertical structure p-type permeable-base organic transistors were proposed and demonstrated. A hole-type organic semiconductor N,N′-diphentyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine was used as emitter and collector. In the permeable-base transistors, the metal base was formed by firstly coevaporating Al and Ca in vacuum and then annealing at 120°C for 5min in air, followed by a thin Al deposition. These devices show a common-base current gain of near 1.0 and a common-emitter current gain of ∼270.

Hybrid Permeable Metal-Base Transistor with Large Common-Emitter Current Gain and Low Operational Voltage

We demonstrate the suitability of N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB), an organic semiconductor widely used in organic light-emitting diodes (OLEDs), for high-gain, low operational voltage nanostructured vertical-architecture transistors, which operate as permeable-base transistors. By introducing vanadium oxide (V2O5) between the injecting metal and NPB layer at the transistor emitter, we reduced the emitter operational voltage. The addition of two Ca layers, leading to a Ca/Ag/Ca base, allowed to obtain a large value of common-emitter current gain, but still retaining the permeable-base transistor character. This kind of vertical devices produced by simple technologies offer attractive new possibilities due to the large variety of available molecular semiconductors, opening the possibility of incorporating new functionalities in silicon-based devices.

High gain in hybrid transistors with vanadium oxide/tris(8-hydroxyquinoline) aluminum emitter

We report the electrical characterization of hybrid permeable-base transistors with tris(8-hydroxyquinoline) aluminum as emitter layer. These transistors were constructed presenting an Al/n-Si/Au/Alq(3)/V2O5/Al structure. We investigate the influence of the V2O5 layer thickness and demonstrate that these devices present high common-base and common-emitter current gain, and can be operated at very low driving voltages, lower than 1 V, in both, common-base and common-emitter modes.

Synthesis, morphology and device characterizations of a new organic semiconductor based on 2,6-diphenylindenofluorene

A new organic semiconductor, 2,6-diphenylindenofluorene (DPIF), was synthesized in four steps with a high overall yield of 49.3%. The morphology of thin films of DPIF that were formed under different substrate temperatures was examined by atomic force microscopy and X-ray diffraction analysis. Two different crystalline phases were found to exist depending on the deposition conditions. The DPIF thin film emits around 500–530 nm, while the OLED based on DPIF emits green light with a maximum output over 150 Cd/m2 under 35 V. Two typical transistor devices, thin-film transistor (TFT) and semiconductor-metal-semiconductor (SMS) transistor, were fabricated and characterized. DPIF shows a weak n-type character from the TFT device measurement, while SMS transistors using DPIF as an emitter behave like permeable-base transistors with low operating voltages in both common-base and common-emitter modes and a feature of current amplification. Our results demonstrate however, that further research efforts are necessary in order to prevent the observed instabilities. These are quite important, considering that the common-emitter mode is widely used in applications requiring not only switching capability, but also current amplification.