Several methods are used in novel ways with newly identified and viable parameters
to decrease the peak transition energies of the pseudomorphic InGaAs/GaAs heterostructures.
These techniques, taken separately or in combination, suffice to permit operation
of light emitting devices at wavelengths of 1.3 m or greater of light-emitting
electro-optic devices. These methods or techniques, by example, include: (1) utilizing
new superlattice structures having high In concentrations in the active region,
(2) utilizing strain compensation to increase the usable layer thickness for quantum
wells with appropriately high In concentrations, (3) utilizing appropriately small
amounts of nitrogen (N) in the pseudomorphic InGaAsN/GaAs laser structure, and
(4) use of nominal (111) oriented substrates to increase the usable layer thickness
for quantum wells with appropriately high In concentrations. In all of the above
techniques, gain offset may be utilized in VCSELs to detune the emission energy
lower than the peak transition energy, by about 25 meV or even more, via appropriate
DBR spacing. Gain offset may also be utilized in some forms of in-plane lasers.
Increased temperature may also be used to decrease peak transition energy (and
therefore the emission energy) by about 50 meV/100 C. All these techniques
are furthermore applicable to other material systems, for example, extending the
emission wavelength for laser diodes grown on InP substrates. Additionally, structures
which utilize the above techniques are discussed.
