Boston University

Bae Systems Information and Electronic Systems Integration Inc.

Boston Microsystems, Inc.

Theodore D Moustakas

Yitao Liao

Charles R Eddy, Jr

Jasper S Cabalu

Kanin Chu

Enrico Bellotti

Liberty L Gunter

Harry L Tuller

Richard Mlcak

Dharanipal Doppalapudi

Richard J Molnar

Adrian D Williams

Mira Misra

Adam Moldawer

Anirban Bhattacharyya

Gordon C Brummer

Joshua Abell

Denis M Nothern

A method of growing an AlGaN semiconductor material utilizes an excess of Ga above the stoichiometric amount typically used. The excess Ga results in the formation of band structure potential fluctuations that improve the efficiency of radiative recombination and increase light generation of optoelectronic devices, in particular ultraviolet light emitting diodes, made using the method. Several improvements in UV LED design and performance are also provided for use together with the excess Ga growth method. Devices made with the method can be used for water purification, surface sterilization, communications, and data storage and retrieval.

High efficiency ultraviolet light emitting diode with electron tunnelling

Semiconductor structures involving multiple quantum wells provide increased efficiency of UV and visible light emitting diodes (LEDs) and other emitter devices, particularly at high driving current. LEDs made with the new designs have reduced efficiency droop under high current injection and increased overall external quantum efficiency. The active region of the devices includes separation layers configured between the well layers, the one or more separation regions being configured to have a first mode to act as one or more barrier regions separating a plurality of carriers in a quantum confined mode in each of the quantum wells being provided on each side of the one or more separation layers and a second mode to cause spreading of the plurality of carriers across each of the quantum wells to increase an overlap integral of all of the plurality of carriers. The devices and methods of the invention provide improved efficiency for solid state lighting, including high efficiency ultraviolet LEDs.

Ultraviolet light emitting diode structures and methods of manufacturing the same

High efficiency ultraviolet light emitting diode with band structure potential fluctuations

The invention provides ultraviolet (UV) light-emitting diodes (LEDs). The UV LEDs can comprise abase layer including p-type SiC or p-type AlGaN, an active layer, and an n-AlGaN layer, wherein the active layer is disposed between the base layer and the n-AlGaN layer. In some embodiments, the absorption losses in p-SiC can be decreased or prevented by incorporating a conductive AlGaN Distributed Bragg Reflector (DBR) between the p-type SiC layer and the active layer. In some embodiments, the n-AlGaN layer can be textured to increase the extraction efficiency (EE). In some embodiments, the external quantum efficiency of the LEDs can be 20-30% or more.

Ultraviolet light emitting diodes

A semiconductor emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate in a nonpolar orientation. The textured layers enhance light extraction, and the use of nonpolar orientation greatly enhances internal quantum efficiency compared to conventional devices. Both the internal and external quantum efficiencies of emitters of the invention can be 70-80% or higher. The invention provides highly efficient light emitting diodes suitable for solid state lighting.

Optical devices featuring nonpolar textured semiconductor layers

Films of III-nitride for semiconductor device growth are planarized using an etch-back method. The method includes coating a III-nitride surface having surface roughness features in the micron range with a sacrificial planarization material such as an appropriately chose photoresist. The sacrificial planarization material is then etched together with the III-nitride roughness features using dry etch methods such as inductively coupled plasma reactive ion etching. By closely matching the etch rates of the sacrificial planarization material and the III-nitride material, a planarized III-nitride surface is achieved. The etch-back process together with a high temperature annealing process yields a planarize III-nitride surface with surface roughness features reduced to the nm range. Planarized III-nitride, e.g., GaN, substrates and devices containing them are also provided.

Planarization of GaN by photoresist technique using an inductively coupled plasma

An etched grooved GaN-based permeable-base transistor structure is disclosed, along with a method for fabrication of same.

GaN-based permeable base transistor and method of fabrication

A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

Optical devices featuring textured semiconductor layers

Growing community of inventors

Dover, MA, United States of America

Theodore D Moustakas