Preliminary results on GaAs-algaas heterostructure quantum Hall resistance standard by the NIM

Till now, quantized Hall devices distributed by the BIPM are used in NIM´s quantized Hall resistance standard. In this paper, we report the preliminary results of quantized Hall devices with GaAs-AlGaAs heterostructures fabricated by ourselves. The device is with AuGeNi contacts for reliability consideration, but the contacts are with relatively large resistances for layer contents and annealing condition was not optimized for 2DEG and low temperature. The large contact resistance caused additional noises and we observed anomalous values for i = 2 quantized Hall step. Next step, The AuGeNi contacts will be optimized.