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Browse Prior Art Database

Full Color Active Matrix Display Based on GaN Lateral Light Emitting Diode Structures

IP.com Disclosure Number: IPCOM000117999D
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 6 page(s) / 257K

Publishing Venue

IBM

Related People

Melcher, RL: AUTHOR [+2]

Abstract

GaN is a wide bandgap semiconductor capable of emitting light of various colors, dependent on the impurities introduced into the crystal (1). Electroluminescence from GaN Light Emitting Diodes (LEDs), both the p-n junction diode and m-i-n diode variety, has been realized in all of the visible colors (1, 2). Therefore, the potential exists to make a full color display from an array of GaN LEDs in which the active impurity responsible for the emission color is laterally varied.

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Full Color Active Matrix Display Based on GaN Lateral Light Emitting
Diode Structures

      GaN is a wide bandgap semiconductor capable of emitting light
of various colors, dependent on the impurities introduced into the
crystal (1).  Electroluminescence from GaN Light Emitting Diodes
(LEDs), both the p-n junction diode and m-i-n diode variety, has been
realized in all of the visible colors (1, 2).  Therefore, the
potential exists to make a full color display from an array of GaN
LEDs in which the active impurity responsible for the emission color
is laterally varied.

      In order to make a practical display from GaN LEDs, it is
necessary to consider new LED structures customized for the needs of
a display technology.  The GaN LEDs which have been demonstrated to
date have all been vertical structures.  A vertical two terminal
device is undesirable for display technology because the array can no
longer be planar, adding additional etching steps, and mesa
structures to the process.  Additionally, address lines must either
follow the non-planar contours which would increase the failure
rates, or separate  planar areas for the address lines must be set
aside, reducing the overall display area dedicated to light
production.

      In addition, a practical display must also be compatible with
an inexpensive active matrix technology in order to realize high
performance.  For example, LCD technology is commonly integrated with
Si thin film transistor arrays fabricated on glass.  A GaN LED based
display would also benefit from an on-board active matrix capability.

      We now address a novel lateral LED structure, which when
realized in GaN, fulfills the above criteria for GaN LED based
display technology.  This is to the best of our knowledge, the first
realization of a lateral LED structure, and could also find
applications in discrete  LED or small LED array applications in GaN
or other semiconductor systems.

      Fig. 1 shows the cross section of the simplest embodiment of a
lateral GaN LED 10.  The lightly shaded region 11 is n-type GaN,
which can be doped during epitaxial growth across the whole wafer.
The darker  shaded region 12 represents the area in which an active
impurity has been  introduced though some sort of mask.  Active
impurities in GaN are deep  levels, and therefore this region 12 is
electrically insulating. This  simplest device structure could be
improved by the introduction of a dielectric layer between the
Schottky contact and the GaN channel to control leakage current and
minimize surface recombination.  During operation, electrons are
injected from the ohmic contacts 13 into the compensated center
region 12 where they recombine radiatively with active  impurity
sites which dictate the resulting photon color.  An important  point
is that the current injection is symmetric, i.e., from either side,
or possibly from all sides (if the active region is circular, the
n-type region 11...