Lehigh University

Hongping Zhao

Nelson Tansu

Guangyu Liu

Ronald A Arif

Yik Khoon Ee

James F Gilchrist

Pisist Kumnorkaew

Jing Zhang

Gensheng Huang

Xiaohang Li

A symmetrical quantum well active layer provides enhanced internal quantum efficiency. The quantum well active layer includes an inner (central) layer and a pair of outer layers sandwiching the inner layer. The inner and outer layers have different thicknesses and bandgap characteristics. The outer layers are relatively thick and include a relatively low bandgap material, such as InGaN. The inner layer has a relatively lower bandgap material and is sufficiently thin to act as a quantum well delta layer, e.g., comprising approximately 6 &#x212b; or less of InN. Such a quantum well structure advantageously extends the emission wavelength into the yellow/red spectral regime, and enhances spontaneous emission. The multi-layer quantum well active layer is sandwiched by barrier layers of high bandgap materials, such as GaN.

Nitride based devices including a symmetrical quantum well active layer having a central low bandgap delta-layer

A light emitting device comprising a staggered composition quantum well (QW) has a step-function-like profile in the QW, which provides higher radiative efficiency and optical gain by providing improved electron-hole wavefunction overlap. The staggered QW includes adjacent layers having distinctly different compositions. The staggered QW has adjacent layers X, wherein X is a quantum well component and in one quantum well layer n is a material composition selected for emission at a first target light regime, and in at least one other quantum well layer n is a distinctly different composition for emission at a different target light regime. X may be an In-content layer and the multiple X-containing layers provide a step function In-content profile.

Staggered composition quantum well method and device

A III-nitride based device provides improved current injection efficiency by reducing thermionic carrier escape at high current density. The device includes a quantum well active layer and a pair of multi-layer barrier layers arranged symmetrically about the active layer. Each multi-layer barrier layer includes an inner layer abutting the active layer; and an outer layer abutting the inner layer. The inner barrier layer has a bandgap greater than that of the outer barrier layer. Both the inner and the outer barrier layer have bandgaps greater than that of the active layer. InGaN may be employed in the active layer, AlInN, AlInGaN or AlGaN may be employed in the inner barrier layer, and GaN may be employed in the outer barrier layer. Preferably, the inner layer is thin relative to the other layers. In one embodiment the inner barrier and active layers are 15 &#x212b; and 24 &#x212b; thick, respectively.

Nitride based quantum well light-emitting devices having improved current injection efficiency

A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

A light emitting device comprising a staggered composition quantum well (QW) has a step-function-like profile in the QW, which provides higher radiative efficiency and optical gain by providing improved electron-hole wavefunction overlap. The staggered QW includes adjacent layers having distinctly different compositions. The staggered QW has adjacent layers Xwherein X is a quantum well component and in one quantum well layer n is a material composition selected for emission at a first target light regime, and in at least one other quantum well layer n is a distinctly different composition for emission at a different target light regime. X may be an In-content layer and the multiple X-containing a step function In-content profile.

A III-Nitride semiconductor LED provides broadband light emission, across all or most of the visible light wavelength spectrum, and a method for producing same. The LED includes a polarization field management template that has a three-dimensional patterned surface. The surface may be patterned with an array of hemispherical cavities, which may be formed by growing the template around a temporary template layer of spherical or other crystals. The method involves growing a quantum well layer on the patterned surface. The topographical variations in the patterned surface of the template cause corresponding topographical variations in the quantum well layer. These variations in spatial orientation of portions of the quantum well layer cause the polarization field of the quantum well layer to vary across the surface of the LED, which leads to energy transition shifting that provides 'white' light emission across a broad wavelength spectrum.

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Bethlehem, PA, United States of America

Hongping Zhao