editor@tjprc.org www.tjprc.org International Journal of Semiconductor Science & Technology (IJSST) ISSN(P): 2250-1576; ISSN(E): 2278-9405 Vol. 4, Issue 2, Dec 2014, 1-12 © TJPRC Pvt. Ltd. NOISE MODELING CIRCUIT OF QUANTUM STRUCTURE TYPE OF INFRARED PHOTODETECTORS MOHAMED B. EL_MASHADE & M. EL_HANASH Department of Electrical Engineering, Faculty of Engineering, Al Azhar University, Nasr City, Cairo, Egypt ABSTRACT Noise is a general property of electrical conductors where it introduces random fluctuations in their currents. Studies of these fluctuations are of great interest because they give information about the charge carriers in the system and their mutual interactions. Quantum well infrared photodetectors QWIPs are very successful devices. They have been developed very quickly and demonstrated large format focal plane arrays with low noise equivalent irradiance, high uniformity, and high operability. Therefore, it is of interest to model its noise behavior under different operating conditions to show to what extent the noise can affect the operation of that attractive device. Our scope in this paper is to derive the noise modeling circuit of QWIP. As a tool for this achievement, it is intuitive to calculate all different current's components, which include dark current, photocurrent, thermal noise current and shot noise currents (generation-recombination noise). Finally, we represent all these noise currents in a simplified electrical circuit to become a one of its basic characteristics. KEYWORDS: QWIP Detectors, Dark Current, Photocurrent, Thermal Noise Current, Photo Shot Noise Current and Dark Shot Noise Current INTRODUCTION The technology of band gap engineering has led to significant advances in the development of new infrared photodetectors. In a bulk type of semiconductor materials, electrons are free to move in any of the three spatial directions. A confining structure may be made by embedding a limited region of one material within another. The difference between allowed electronic states for the two materials forms a barrier to free electron movement. If any dimension of the structure approaches the wavelength of an electron, quantum effects will arise. Quantum structures of semiconductor materials have the property of confining the mobility of electrons. Each one of the three dimensions of the bulk material may be thinned conceptually to yield the three classes of quantum structures. Making the structure thin along only one axis results in a two dimensions layer called a quantum well. If thinned along any two of three axes, a one dimension quantum wire is produced. Thinning along the final axis leads to a zero dimension structure known as quantum dot. The design of quantum well devices was originated from the suggestion that a hetero structure consisting of alternating ultrathin layers of two semiconductors with different band gaps should exhibit some novel useful properties [1, 2]. The band-edge potential varies from layer to layer as a result of the difference in the band gaps and a periodically varying potential is produced in the structure with a period equal to the sum of the widths of two consecutive layers [3]. This is because of the importance of the developed device in achieving novel characteristics in the fields of optical communications, thermal imaging and sensor networking, etc. Recently infrared photo detectors have been the focus of