High-power room-temperature continuous wave operation of type-I In(Al)GaAsSb/GaSb diode lasers at wavelengths greater than 2.5 μm

We have fabricated and characterized 2.7- and 2.8-μm wavelength In(Al)GaAsSb/GaSb two-quantum-well diode lasers. The material was grown using molecular-beam epitaxy. All lasers have 2-mm cavity lengths and 100 μm apertures. Continuous wave operation up to 500 mW was recorded at 16°C from 2.7-μm lasers, while 160 mW was obtained from 2.8-μm lasers. Threshold current densities as low as 350 A/cm ² were recorded from 2.7-μm lasers with external quantum efficiencies of 0.26 photon/electrons. The maximum wall-plug efficiency was 9.2 % at a current of 2.4 A. A peak power of 2.5 W was recorded in the pulsed-current mode operation at 20°C at 2.7 μm and 2 W at 2.8 μm. Characteristic temperatures of T ₀ = 71 K and T ₁ = 86 K were measured from the 2.7-μm devices. T ₀ = 59 K and T ₁ = 72 K for the 2.8-μm lasers. The devices have differential series resistances of about 0.18 Ω with estimated thermal resistances of about 5 K/W. Measurements of gain, losses, threshold current, device efficiency and spontaneous emission of the lasers show that it is the hole leakage from QWs into the waveguide, and not Auger recombination that limits CW room temperature output power of long wavelength GaSb-based type-I QW lasers at least up to wavelengths of 2.8 μm. A design approach to extend the operating wavelength of high power In(Al)GaAsSb/GaSb lasers to more than 3 μm is discussed.