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Room temperature yellow InGaAlP quantum dot laser
We report simulation of the conduction band alignment in tensile–strained GaP–enriched barrier structures and
experimental results on injection lasing in the green–orange spectral range (558–605 nm) in
(AlxGa1–x)0.5In0.5P–GaAs diodes containing such barriers. The wafers were grown by metal–organic vapor phase
epitaxy side–by–side on (8 1 1)A, (2 1 1)A and (3 2 2)A GaAs substrates, which surface orientations were strongly
tilted towards the [1 1 1]A direction with respect to the (1 0 0) plane. Four sheets of GaP–rich quantum barrier
insertions were applied to suppress the leakage of non–equilibrium electrons from the gain medium. Two types
of the gain medium were applied. In one case 4–fold stacked tensile–strained (In,Ga)P insertions were used.
Experimental data shows that self–organized vertically–correlated quantum dots (QDs) are formed on (2 1 1)A–
and (3 2 2)A–oriented substrates, while corrugated quantum wires are formed on the (8 1 1)A surface. In the
other case a short–period superlattice (SPSL) composed of 16–fold stacked quasi–lattice–matched 1.4 nm–thick
In0.5Ga0.5P layers separated by 4 nm–thick (Al0.6Ga0.4)0.5In0.5P layers was applied. Laser diodes with 4–fold
stacked QDs having a threshold current densities of ∼7–10 kA/cm2 at room temperature were realized for both
(2 1 1)A and (3 2 2)A surface orientations at cavity lengths of∼1 mm. Emission wavelength at room temperature
was ∼599–603 nm. Threshold current density for the stimulated emission was as low as ∼1 kA/cm2. For
(8 1 1)A–grown structures no room temperature lasing was observed. SPSL structures demonstrated lasing only
at low temperatures<200 K. The shortest wavelength (558 nm, 90 K) in combination with the highest operation
temperature (150 K) was realized for (3 2 2)A–oriented substrates in agreement with theoretical predictions.