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Quantum Well Visible AlGaInP Light Emitting Diodes

IP.com Disclosure Number: IPCOM000108297D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 4 page(s) / 125K

Publishing Venue

IBM

Related People

Heuberger, W: AUTHOR [+3]

Abstract

High efficiency/brightness visible AlGaInP light-emitting diodes (LEDs) with specially designed quantum wells as active recombination region are described.

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Quantum Well Visible AlGaInP Light Emitting Diodes

       High efficiency/brightness visible AlGaInP light-emitting
diodes (LEDs) with specially designed quantum wells as active
recombination region are described.

      The quantum well or multi-quantum well structure employed in
LEDs has different inherent advantages in comparison to conventional
LEDs having thick active heterostructure recombination layers. Caused
by the quantum size effect, the diode is emitting shorter wavelength
and the reduced radiative lifetime in quantum wells increases the
quantum efficiency. The self-absorption of the LED is reduced by the
smaller volume of the well and the quantum well allows introducing
strain. By the employment of compressive or tensile strained quantum
well(s), it is possible to affect the intensity of the emitted light
and the bandgap and thus the wavelength. This dependance has, e.g.,
been investigated and reported in (1).

      Still a further phenomena that has been found to substantially
affect both the intensity and the wavelength of LED emitted light is
that some semiconductor materials, especially AlGaInP
      -  exist in several phases, i.e., ordered and disordered, which
differ in the structural arrangement of group III species,
      -  the bandgap energy EG increases when changing from the
ordered to the disordered phase,
      -  and to grow under standard MOVPE growth conditions and
substrate orientation in the ordered phase whereas, in case of
strongly misoriented substrates, the disordered phase is obtained.

      Two relevant articles relating to this phenomena are (2,3).

      Fig. 1 shows the schematic layer sequence of the diodes herein
referred to. Different AlGaInP/GaInP multi-quantum well
heterostructures with unstrained, tensile strained and compressive
strained GaInP quantum wells have been grown by MOVPE on (100) 20 off
oriented and (311)A oriented GaAs substrates. Room temperature
photoluminescence (PL) measurements, using a 10mW Ar-laser, were made
and the results are shown in Fig. 2. Temperature-dependent PL
measurements show that the 300K PL of the samples shown in Fig. 3
mainly ori...