9 In 1x Ga x As a next generation material for photodetectors Dr.B.K.Mishra 1 , Lochan Jolly 2 , S.C.Patil 3 1,2 Thakur college of Engineering and Technology/EXTC, Mumbai, India 3 Parshvanath College of Engineering/EXTC,Mumbai,India Email: drbk.mishra@thakureducation.org Email: lochan.jolly@thakureducation.org Email: sanjay.c.patil@gmail.com ! " ! ! #$ % ! —&’ ’ ’ % I. INTRODUCTION With silicon VLSI technology approaching the limits of scaling and miniaturization, new material systems and device technologies are under investigation for improved speed and circuit compaction. Among the most promising of these are the resonant tunneling devices based on Gallium Arsenide (GaAs), Indium Phosphide (InP), and other IIIV semiconductor materials alloys like In 1x Ga x As. The electrical performance of these devices is dominated by quantum effects. The devices contain quantumwell structures of nanometer dimensions comparable with the electron wavelength. Consequently, the wave nature of the electrons becomes important in determining the device electrical characteristics and these characteristics are very different from those of larger semiconductor devices such as the conventional MOSFET. ! " ! #$ ! Wavelength(Å) Figure 1.Attenuation Vs Wavelength[1] A strong interest has been created in the study of optical effect in highspeed devices due to their potentiality in fiber optical communication and optical device integration. Both experimental and analytical studies have been carried out by different investigators on the effect of illumination in GaAs MESFET as they show significant effect of incident light on the electrical parameters of the devices for applications in circuits for working in first window for optical communication. But as the rate of data transmission is increasing we require large bandwidth photodetector for working in second and the third window for optical communication as shown in Figure 1. GaAs is a compound consisting of Ga atoms bonded to As atoms. An alloy which is made of two compounds can give required characteristics to the material according to the mole fraction of the compounds used. In 1x Ga x As is an alloy compound consisting of InAs and GaAs with a mole ratio of (1x):(x). The bonds in GaAs and InAs have characteristics intermediate to those usually associated with the covalent and ionic terms. So according to the requirement we can set the composition of the components GaAs and InAs to have required characteristics [1]. Recently, In 1x Ga x As structures have been widely studied for ultrahighspeed device application especially for second and third window of operation for optical communication. In 1x Ga x As has high intrinsic carrier concentration with a high carrier mobility and saturated velocity. This material can detect and amplify radiation of wavelength within the range of 1.3–1.6 Dm which is of recent interest in fiberoptic communication systems [1]. In this paper, we have calculated the effect of optical illumination on the ultra high speed In 0.57 Ga 0.43 As MESFET. Previously, studies have been reported on the effect of illumination on GaAs MESFET considering opaque or transparent or semitransparent Schottky gate. In this paper a comparative study of the In 0.57 Ga 0.43 As and GaAs is also done to have a better understanding of the application of the device in different windows. The photovoltage is developed across the Schottky junction which enhances the charge concentration of the channel region. The excess carriers are solved using the continuity equations for electrons and holes. The effect of radiation on IV characteristics has been presented. The theory is presented below. Cyber Journals: Multidisciplinary Journals in Science and Technology, Journal of Selected Areas in Microelectronics (JSAM), April Edition, 2011