The temperature dependence of threshold current and quantum efficiency for GaxIn1- xP (x equals 0.4, 0.6; (lambda) equals 680, 633 nm) single 80 angstrom quantum well lasers is analyzed using a model for the electron leakage current. This model fits the experimental data, correctly describing the rapid increase in threshold and drop in quantum eficiency as temperature increases. Also it indicates that the drift component of the electron leakage current is important, because of the poor p-type conductivity in AlGaInP. In addition, a single quantum well Ga0.5+(delta )In0.5-(delta )P/(AlGa)0.5P laser structure is demonstrated, which can provide similar gain in both polarizations. The slightly-tensile- strained quantum well has the light hole ground state, which gives the lowest transparency current for TM-mode gain. However, the TE-mode gain is dominant at high drive currents. The gain-current relationships have been characterized for each polarization, and found to cross at a modal gain value of 25 cm-1. Lasers whose threshold gain is near this crossover value were found to emit in either one or both polarizations, with a very wide range of polarization assymetry possible. A simple QW gain model can be used to describe this behavior.