Chandra Mohan Singh Negi

Theoretical Analysis of Resonant Cavity p-Type Quantum Dot Infrared Photodetector

A theoretical analysis for resonant cavity enhanced p-type quantum dot (QD) infrared photo-detector that uses intervalence subband transitions in InxGa1-xAs/GaAs QDs is presented. Multiband effective mass k.p model with the strain effect is used to calculate valance subband energy levels. Photocurrent spectra, response wavelength, and dark current density of QD infrared detector have been calculated. The calculations have been performed for a wide range of dot sizes, compositions, dot height, bias voltages, and temperatures. The effect of QD height, radius, and composition on the response of the photodetectors has been analyzed and some criteria for performance improvement have been suggested.

Temperature Effect on Optical Gain of CdSe/ZnSe Quantum Dots

In this work, theoretical formulation for the computation of electronic structure and gain spectra of CdSe/ZnSe quantum dot has been developed in the framework of multi-band k.p. approach. The optical gain of CdSe/ZnSe quantum dot has been determined. The gain is found to increase with carrier density but it is found to decrease as we increase the temperature.

Analysis of electromagnetically induced transparency-based quantum dot infrared photodetectors

A quantum dot infrared (IR) photodetector based on intraband optical transitions among the various states within the valence band by considering the principle of electromagnetically induced transparency (EIT) is proposed and theoretically investigated. Absorption spectra of the probe beam and its dependence on the control beam and IR signal under the conditions of EIT have been studied. The incident IR signal itself does not generate any photocurrent. However, profound modification of the absorption characteristics of the probe beam by incident IR signal intensity leads to photocurrent generation in the proposed photodetector. Thermal characterization of the photodetector has been carried out through the evaluation of the temperature dependence of the quantum efficiency of the device.

Effect of Shape Anisotropy and Size on the Electronic Structure of CdSe/ZnSe Quantum Dots

The effect of shape anisotropy and size on the electronic structure of CdSe/ZnSe quantum dots is theoretically investigated. The quantum dot is modeled by assuming a parabolic confinement along xy plane and by finite well potential due to band offset along growth (z) direction. The energy eigenvalues and wave functions of holes in multivalence band are computed by numerical diagonalization of 4 × 4 k.p Luttinger Hamiltonian. The wave functions thus obtained are used for calculating dipole matrix elements to analyze the degree of linear polarization and allowed transitions between multivalence band and conduction band. The effect of variation of dot size, dot height, and shape anisotropy factor on the electronic structure is also analyzed. We observe that the size and shape anisotropy of quantum dot play a significant role in determining their electronic structure.

Resonant cavity far infrared photo-detector based on self-assembled InAs/GaAs quantum dots

In this paper, a novel design for far infrared resonant cavity enhanced quantum dot photo-detector (RCE QDP) based on bound-to-bound intervalence subband transitions in self assembled InAs/GaAs quantum dots (QDs) is presented. The device structure consists of QDs active layers inserted between two distributed Bragg reflectors (DBRs). Quantum efficiency is calculated as a function of wavelength for different reflectivity of mirrors. Dark current is calculated as a function of the voltage for different value of temperature and QD radius.

Characteristics of II–VI Quantum Dot Infrared Photo-Detectors

We theoretically investigate the performance of a II–VI ZnCdSe/ZnSe- based quantum dot infrared photodetector (QDIP) utilizing intersubband hole transitions in the valence band of the QDs to absorb infrared radiation. The analysis starts with the computation of band structure via multi-band effective mass model based on the Luttinger-Kohn Hamiltonian with the inclusion of strain effects. The theoretical formulation is further used to determine the spectral responsivity and dark current characteristics of the QDIP.

Performance investigations of multicolor, broadband quantum dot infrared photodetector

Multiband detectors have many advantages compared with the single band detectors. In this paper a multi color, broad band infrared detector is proposed and analyzed. This multilayer quantum dot infrared detector utilizes the inter-valence band transitions in the InGaAs quantum dots to achieve the multicolor broad band response. Energy eigen values and wave functions of the hole states are determined by the numerical diagonalization of the Luttinger Kohn Hamiltonian. Absorption spectra is calculated by summing over the absorption due to transition from the heavy hole ground state to the all possible states. Then self-consistent numerical calculation method is used to determine the photocurrent and spectral responsivity of multilayer QDIP.

Shape and Size Dependent Electronic Properties of GaAs/AlGaAs Quantum Dots

We have theoretically investigated the effect of shape anisotropy and size on electronic structure of GaAs/AlGaAs quantum dots (QDs). The quantum dot is modeled by anisotropic parabolic confinement potential in the plane perpendicular to the growth direction while the confinement along the growth direction is modeled as quantum well potential. The Luttinger Hamiltonian formulation has been used to account for the valence subband mixing. The electronic structure is calculated by numerical diagonalization of Luttinger Hamiltonian using the harmonic oscillator basis functions. The calculations for hole energies and transition energies have been carried out over wide range of size and shape of QDs. The results show that transition energy of QDs decreases with the height of QDs. Significant variation in the hole energy is observed with the change in anisotropy. We also observe that shape anisotropy and mixing have significant effect on the energy states.