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Monolithic GaN Light Emitting Diode Arrays for Display Illumination

IP.com Disclosure Number: IPCOM000118126D
Original Publication Date: 1996-Sep-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 100K

Publishing Venue

IBM

Related People

Strite, SC: AUTHOR

Abstract

GaN is a wide bandgap semiconductor which is known to be capable of emitting light of various colors, dependent on the impurities introduced into the crystal (1). Electroluminescence from GaN LEDs, both of the p-n junction diode and m-i-n diode variety, have been realized in all of the visible colors (1, 2). Therefore, the potential exists to make a full color light source from an array of GaN LEDs in which the active impurity responsible for the emission color is laterally varied. Such light sources could be useful as illumination for transmissive and reflective display embodiments.

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Monolithic GaN Light Emitting Diode Arrays for Display Illumination

      GaN is a wide bandgap semiconductor which is known to be
capable of emitting light of various colors, dependent on the
impurities introduced into the crystal (1).  Electroluminescence from
GaN LEDs, both of the p-n junction diode and m-i-n diode variety,
have been realized in all of the visible colors (1, 2).  Therefore,
the potential  exists to make a full color light source from an array
of GaN LEDs in which the active impurity responsible for the emission
color is laterally  varied.  Such light sources could be useful as
illumination for transmissive and reflective display embodiments.

      Fig. 1 shows the cross section of a sub-section of a GaN LED
light source.  The lightly shaded regions are n-type GaN, which could
be doped during epitaxial growth across the whole wafer.  The darker
shaded regions are labelled corresponding to the color of their
active impurity transitions.  The laterally varied impurity
distribution is introduced in several steps, through masking layers.

      Monolithic arrays comprising multiple sets of red, green and
blue GaN LEDs could be useful as light sources, especially for
display illumination.  The lamp could easily be wired such that at a
given time,  only LEDs of one color type are active.  This eliminates
the need for a  color filter array or sub-pixels.  As a result,
individual pixels can occupy the area corresponding to three
sub-pixels in the conventional approach.  Pixels of increased area
are more transmissive, which increases the optical efficiency.  This
approach is commonly referred to  as field sequential color and has
long been a goal.

      The fact that a GaN light source can be comprised of numerous
LEDs adds increasing flexibility and efficiency to illumination
schemes based thereon.  For example, the light source could be
partitioned into  independently wired quartiles, each responsible for
illuminating a respective quarter of the Spatial Light Modulator
(SLM).  In the case that blue light is only required in one quarter
of the image, the GaN light source could be dr...