2 μm InGaSb/AlGaAsSb single quantum well(SQW) laser with low threshold current density of ~131 A/cm2 and its ideality factor n was presented. The ideality factors n of the central p-n junction and the n-GaSb/metal junction sum up to be the total ideality factor n of the laser. The total ideality factor n decreases from 4.0 to 3.3 when the temperature was increased from 20 to 80 ℃. The results are in good agreement with the applied theoretical model as well as the ideality factor n of the individual GaSb-based junctions(p-n junction, GaSb/metal junction etc.).