Modeling of Charge Transport in a Hybrid Metal / Organic / Inorganic Device
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1029-F01-08
Modeling of Charge Transport in a Hybrid Metal / Organic / Inorganic Device Henry Alberto Méndez Physics, Pontificia Universidad Javeriana, Cra 7 No 43-82 Ed.52 Of.606, Bogota, Colombia ABSTRACT A Metal / Organic / Inorganic semiconductor heterostructure was built and characterized in situ under ultra-high vacuum conditions (UHV). The aim was to investigate the influence of a perylene-derivative organic thin film on the transport electronic properties of Schottky Ag / GaAs diodes. The device was studied using a combination of photoemission spectroscopy (PES) and electrical measurements. The obtained results were discussed using the analytical expressions of a trapped charge limited current (TCLC) model. INTRODUCTION Last decade of the past century was characterized by an exponentially increasing effort to bring devices based on organic materials into the market [1]. Several applications are routinely available for use. Pioneering this trend is the novel flat panel display technology based on organic light emitting diodes (OLEDs) [2]. More recently, a new generation of organic-based devices are increasing performance (i.e. organic field effect transistors - OFET), being close to reach the point to be commercialized, while others are in a design or testing phase for novel applications: fuel cells, organic-based solar cells and organic-based memories, for instance. Almost without exception, the basic structure of most of these devices consists of one or more layers of the active organic materials sandwiched between two electrodes [3]. Semiconducting or metallic electrodes inject or remove charge from the devices and efficient charge transport across the organic / inorganic interface is critical to the device performance. Thus, the commercial success of organic electronics will strongly depend on making scientific progress in understanding the injection process and the nature of the junction. The performance of such hybrid devices are based not only in the properties of the organic layer itself (i.e. flexibility of intermolecular bonds), but also on those that can be derived from metal / organic and / or organic / inorganic interfaces. In the present work, a device based in one organic layer with both kinds of hybrid interfaces was built under ultra-high vacuum conditions (UHV) and their electronic properties characterized in situ with the aim of understanding the electronic transport mechanisms through the device. EXPERIMENT The basic structure of an organic-modified Ag / GaAs Schottky diode is sketched in figure 1.
Figure 1. Metal / Organic / Inorganic heterostructure. A piece of an n-type GaAs wafer (5×5 mm2) with a doping concentration of n ~ 1 × 1016 cm-3 is cleaned and etched with HCl (38%) for 30 seconds, in order to remove the native insulating GaAs oxide layer. Then, it is attached to a cupper plate using a Ga-In alloy paste for having an ohmic contact and transferred to a vacuum chamber. The GaAs substrate normally requires annealing for completing the passivation procedure at 350°C under the ac
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