Preparation of 1.78-μm wavelength Al0.2Ga0.8Sb/GaSb double-heterostructure lasers by molecular beam epitaxy

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Abstract
As the losses due to Rayleigh scattering decrease at a rate of λ4 with increasing wavelength λ, the future generation of optical fibers, light sources, and detectors may well be operating at still longer wavelength beyond 1.55 μm. The present letter reports the first preparation of Al0.2Ga0.8Sb/GaSb double‐heterostructure (DH) lasers by molecular beam epitaxy (MBE) operating at 1.78 μm. For AlxGa1−xSb with x≲0.1, room‐temperature photoluminescent intensity and linewidth similar to those of bulk GaSb substrate of similar carrier concentration were obtained. The Al0.2Ga0.8Sb/GaSb DH laser wafers grown by MBE have smooth, featureless, mirror‐reflecting surfaces. Reflection high‐energy electron diffraction study shows that the abrupt Al0.2Ga0.8Sb/GaSb interfaces were atomically smooth. Initial threshold current measurements gave a pulsed threshold current density of 3.4 kA/cm2 for a diode of 380×200 μm and an active GaSb layer of 0.33 μm.