A two-step channelIn0.1Ga0.9As/In0.25Ga0.75Asheterostructure real-space transfer transistor grown by low-pressure metalorgonic chemical vapor deposition is implemented. By virtue of &dgr; doping, shallow ohmic contacts and two-step channel, a high peak-to-valley current ratio up to 260 000 at 300 K can be obtained at low collector voltage(Vc=3 V).Moreover, from Shubnikov–de Haas (SdH) measurements, we observe a positive persistent-photoconductivity effect and variations of quantum lifetime. The SdH result is in good agreement with the critical drained-to-source onset voltage of negative differential resistance. ©1997 American Institute of Physics.