ABSTRACT
This chapter describes the theoretical framework and numerical modeling of Quantum well infrared photodetectors (QWIPs). QWIPs are based on optical transitions among quantized states in the conduction band of the quantum wells (QWs). A QWIP uses multiple quantum well structures to detect light. These structures are realized by growing alternate material layers of different bandgaps on a suitable substrate. The chapter analyzes the role of photocurrent and dark current in affecting the sensitivity of a QWIP focal plane array. The dark current of a QWIP can be qualitatively separated into three main components. They are direct tunneling between adjacent ground states, thermally assisted tunneling (TAT) near the top of the barrier, and thermionic emission over the barrier. The TAT current originates from the finite thermal spreading of in-plane electron energy. Upon a scattering process, the in-plane energy combines with the out-of-plane energy, with which the electron tunnels more efficiently through the QW barrier.
