An InGaAsP-InP transistor laser (TL) working at 1.5 μm and its epitaxy structure with MQW active layer buried between unsymmetrical upper and lower waveguides in base region has been designed and modeled. The simulation result shows that the proposed TL has good optical and lateral electrical current confinement. The result of epitaxial experiment by metalorganic chemical vapor deposition (MOCVD) shows that the diffusion of doped Zn2+ from heavily doped base contactor layer to active waveguide can induce serious degradation of quantum wells. By modeling the Zn2+ diffusion from heavily doped base contactor layer, a gradient doping profile with an average doping density of 1 ( 1018 cm-3 in the base contact layer has been used in the epitaxy process to constrain the Zn2+ diffusion to quantum wells. The test result of the epitaxy material has demonstrated high PL intensity at 1.51 μm and clear satellite diffraction peaks in the XRD spectrum.