Modeling of Current-Voltage Characteristics of the Photoactivated Device Based on SOI Technology

An analytical model of the silicon on insulator photoactivated modulator (SOI-PAM) device is presented in order to describe the concept of this novel device in which the information is electronic while the modulation command is optical. The model, relying on the classic Shockley’s analysis, is simple and useful for analyzing and synthesizing the voltage-current relations of the device at low drain voltage. Analytical expressions were derived for the output current as function of the input drain and gate voltages with a parameterization of the physical values such as the doping concentrations, channel and oxide thicknesses, and the optical control energy. A prototype SOI-PAM device having an area of 4？μm × 3？μm with known parameters is used to experimentally validate and support the model. Finally, the model allows the understanding of the physical mechanisms inside the device for both dark and under illumination conditions, and it will be used to optimize and to find the performance limits of the device. 1. Introduction Silicon-based nanophotonic devices have attracted appreciable attention and effort because of their potential applications in silicon-integrated circuits. Although silicon may be not the ideal platform for optical devices, the usage of silicon is mandatory for the generation of optoelectronic integrated circuitry. The quality of commercial silicon on insulator (SOI) wafers driven by the microelectronics industry still continues to improve while the cost continues to decrease. Moreover, as previously mentioned the compatibility with silicon integrated circuits manufacturing is an important reason for this interest in silicon photonics [1]. The optical capabilities are used to overcome some limits of the non optical devices. Those capabilities are high propagation velocity, reduced cross talks and absence of noise coupled by electrical inductance and capacitance [2–4]. Such devices can operate at very low operational power and have parallel processing capabilities [5, 6]. In this paper, we present the first analytic model of the previously presented hybrid optical-electrical device, the silicon on insulator photo-activated modulator (SOI-PAM) [7]. As deduced from its name, the device is controlled by optical command. like a junction field effect transistor (JFET), the information current flows between two terminals (source and drain) in a silicon channel. The device concept relays on the fact that the thickness of depletion layer in the channel, which affects the information current, can be controlled through external illumination and not