The high quality modulation doped GaAs/N-AlGaAs heterostructures have been grown by a vertical molecular beam epitaxy system (MBE). Electron mobility of two dimentional electron gas (2DBG) at 4.2 K has reached as high as 4.26×105cm2/V·s (in the dark) and 5.9×105cm2/V·s (under light illumination). The polaron mass of 2DEG was determined by analysis of oscillatory resistance change of magnetophonon resonance in pulsed magnetic field. The mobility enhancement of 2DEG in low field and quantum Hall effect in high field at 4.2 K were also studied.