Linear bounded potential model for semiconductor band bending

We propose a simple but unexplored model for the semiconductor band bending with the aim to obtain a relatively simple expression to calculate the energy spectrum for the confined levels and the analytical expressions for wave-functions. This model consists of a linear potential but it is bounded or trimmed in energy unlike the well known wedge potential model. We present exact solutions for this potential in the frame of the effective mass approximation and they are valid for electron or hole confinement potential. This model provides a more adequate physical scenario than the wedge potential since it takes into account the charge balance involved in the band bending potential. These results allow to treat confined potential problems as in the case of a two-dimensional electron gas (2DEG) in a simplified way. We discuss the application of this approximation to the recombination time of electrons an holes and for the Franz-Keldysh effect.

Comparative Study of Si-Ge-Sn Resonant Cavity Enhanced Heterojunction Bipolar Phototransistor (RCE-HPT) under Quantum Confined Stark Effect (QCSE) and Franz Keldysh Effect (FKE) at 1.55 µm

Group-IV and their alloy based Heterojunction Bipolar Phototransistors (HPTs) are of immense interest in recent day optical communication. In this paper first resonant cavity enhanced heterojunction bipolar phototransistor (RCE-HPT) with Ge0.992Sn0.008/Si0.30Ge0.61Sn0.09 Quantum Well/barrier structure under Quantum Confined Stark Effect (QCSE) has been evaluated. Further the bulk GeSn absorption region has been considered instead of QW/barrier structure and estimated the Franz Keldysh Effect (FKE). Finally different RCE-HPT related parameters such as quantum efficiency-bandwidth product, responsivity, collector current and optical gain have been studied and compared under QCSE and FKE.

Impact of a surface on the electro-reflectance spectra of n-Si(110) and their polarization anisotropy

The electro-reflectance spectra, including their polarization dependencies were analyzed for n-Si(110) in the energy range of 2.9-3.8 eV. Based on the optical anisotropy of electro-optical effect, two contributions originated from a surface, (isotropic part relates to the linear electro-optical effect which inherent for (110) surface) and bulk, (anisotropic part relates to the Franz–Keldysh effect) were identified and separated. The presence of such extreme is explained by the zero value of the electron wave function on the surface and (or) the structure gettering of the free carriers.

Light interactions with semiconductors

This chapter examines how electromagnetic waves—light, photons—interact with semiconductors through coupling between the electromagnetic wave and dipoles of various kinds and analyzed via a dipole interaction Hamiltonian. Phenomena in the energy range of micro eV to several eVs are explored, stressing surface interactions, absorption, emission and luminescence. The first involves coupled plasmon interactions. Absorption and emission arise across energy and through multiple mechanisms. Free carrier processes are pronounced for low energy. Direct electron-photon interactions—a direct transition—can involve allowed transitions and forbidden transitions across the gap. Indirect transitions of both these varieties can arise in phonon-assisted processes. Oscillator strength is fleshed out. Field dependence, doping dependence and temperature dependence are analyzed, broadening the discussion to the Franz-Keldysh effect as well as dependence due to impurities, excitons, plasmons and crystal oscillations, to unravel the dielectric function and reflectivity’s behavior at high frequencies and restrahlen often observed.