Low threshold heterojunction AlGaAsSb/GaSb lasers in the wavelength range of 1.5 - 1.8 µm

Double heterostructures of AlGaAasb quaternary alloys on (100)-GaSb substrates were grown by LPE technique and were studied as laser devices. The active layer thickness was in the range 0.3-1.5 μm. Threshold current density for 300 K was as low as 15-2.5 kA/cm
²
in the wavelength range of 1.7-1.8 μm. Shorter wavelength lasers showed a higher threshold. At 77 K CW lasing was observed in the wavelength range up to 1.41 μm. Optical confinement calculations in DH lasers have been supported by observations of the angular distribution of the laser emission, depending on the cladding layer composition and the active layer composition and thickness. The vertical beam spreading angle passed the maximum of 50° at a thickness of the active layer of about 0.8 μm. Temperature dependence of the threshold current has been measured between 100 and 300 K and the exponent temperature constant T
₀
was found to be close to 60-80 K in typical diodes. "Kinky" behavior of the light output power versus current was observed in the stripe-geometry lasers, as well as in the broad-area lasers.