Rajaram Bhat

Bio: Rajaram Bhat is an academic researcher from Corning Inc.. The author has contributed to research in topics: Quantum well & Laser. The author has an hindex of 57, co-authored 448 publications receiving 13404 citations. Previous affiliations of Rajaram Bhat include University of Illinois at Urbana–Champaign & Telcordia Technologies.

Extreme selectivity in the lift‐off of epitaxial GaAs films

Abstract: We have discovered conditions for the selective lift‐off of large area epitaxial AlxGa1−xAs films from the substrate wafers on which they were grown. A 500‐A‐thick AlAs release layer is selectivity etched away, leaving behind a high‐quality epilayer and a reusable GaAs substrate. We have measured a selectivity of ≳107 between the release layer and Al0.4Ga0.6As. This process relies upon the creation of a favorable geometry for the outdiffusion of dissolved H2 gas from the etching zone.

Optical properties of AlxGa1−x As

Abstract: We report pseudodielectric function 〈e〉 data for AlxGa1−xAs alloys of target compositions x=0.00–0.80 in steps of 0.10 grown by liquid‐phase epitaxy and measured by spectroellipsometry. Cleaning procedures that produce abrupt interfaces between the technologically relevant alloys x≤0.5 and the ambient are described. The 〈e2〉 data are corrected near the fundamental direct absorption edge by a Kramers–Kronig analysis of the 〈e1〉 data to circumvent a limitation of the rotating‐analyzer ellipsometric technique. The results and the associated pseudooptical functions 〈n〉, 〈R〉, and 〈α〉 are listed in tabular form. Accurate values of the E0 and E1 threshold energies are determined from these spectra by Fourier methods. From these values, and from similar values for a GaAs‐capped AlAs sample grown by organometallic chemical vapor deposition, the dependencies of the E0 and E1 interband critical point energies on nominal composition are obtained. Cubic polynomial representations of these dependences are determined to...

Stimulated emission in semiconductor quantum wire heterostructures.

Abstract: We report the first observation of stimulated emission in quasi-one-dimensional semiconductor quantum wires Amplified spontaneous emission and stimulated emission spectra of the GaAs/AlGaAs quantum wires exhibit fine structure arising from transitions between lateral, one-dimensional electron and hole subbands The observed subband separations, \ensuremath{\sim}10 meV, are consistent with the calculated ones

Light extraction from optically pumped light-emitting diode by thin-slab photonic crystals

Abstract: We describe a promising thin-slab light-emitting diode (LED) design, which uses a highly efficient coherent external scattering of trapped light by a two-dimensional (2D) photonic crystal. The light generation region was an unpatterned heterostructure surrounded by the light extraction region, a thin film patterned as a 2D photonic crystal. A six-fold photoluminescence enhancement was observed compared to an unpatterned thin film LED. That corresponded to 70% external quantum efficiency.

Nearly ideal electronic properties of sulfide coated GaAs surfaces

Abstract: We have discovered that a class of inorganic sulfides [Li2S, (NH4)2S, Na2S⋅9H2O, etc.] imparts excellent electronic properties to GaAs surfaces. The surface recombination velocity at the interface between Na2S⋅9H2O and GaAs begins to approach that of the nearly ideal AlGaAs/GaAs interface. We propose the formation of a robust covalently bonded sulfide layer to explain the favorable electronic quality of such interfaces.

Inhibited Spontaneous Emission in Solid-State Physics and Electronics

Abstract: It has been recognized for some time that the spontaneous emission by atoms is not necessarily a fixed and immutable property of the coupling between matter and space, but that it can be controlled by modification of the properties of the radiation field. This is equally true in the solid state, where spontaneous emission plays a fundamental role in limiting the performance of semiconductor lasers, heterojunction bipolar transistors, and solar cells. If a three-dimensionally periodic dielectric structure has an electromagnetic band gap which overlaps the electronic band edge, then spontaneous emission can be rigorously forbidden.

Band parameters for III–V compound semiconductors and their alloys

Abstract: We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Nearly 100% internal phosphorescence efficiency in an organic light emitting device

Abstract: We demonstrate very high efficiency electrophosphorescence in organic light-emitting devices employing a phosphorescent molecule doped into a wide energy gap host. Using bis(2-phenylpyridine)iridium(III) acetylacetonate [(ppy)2Ir(acac)] doped into 3-phenyl-4(1′-naphthyl)-5-phenyl-1,2,4-triazole, a maximum external quantum efficiency of (19.0±1.0)% and luminous power efficiency of (60±5) lm/W are achieved. The calculated internal quantum efficiency of (87±7)% is supported by the observed absence of thermally activated nonradiative loss in the photoluminescent efficiency of (ppy)2Ir(acac). Thus, very high external quantum efficiencies are due to the nearly 100% internal phosphorescence efficiency of (ppy)2Ir(acac) coupled with balanced hole and electron injection, and triplet exciton confinement within the light-emitting layer.

Optical microcavities

Abstract: Microcavity physics and design will be reviewed. Following an overview of applications in quantum optics, communications and biosensing, recent advances in ultra-high-Q research will be presented.

Diode Lasers and Photonic Integrated Circuits

Abstract: Ingredients. A Phenomenological Approach to Diode Lasers. Mirrors and Resonators for Diode Lasers. Gain and Current Relations. Dynamic Effects. Perturbation and Coupled--Mode Theory. Dielectric Waveguides. Photonic Integrated Circuits. Appendices. Index.