Highly reproducible tunnel currents in MBE-grown semiconductor multilayers
Tunnel currents through semiconductor tunnel barriers have proved very difficult to control to the extent that device-to-device variability and wafer-to-wafer irreproducibility have prevented electronic devices based on tunnelling from ever going into production. With reference to a single tunnel barrier of AlAs in a GaAs multilayer structure with an asymmetric doping profile, it is shown that, with careful attention to detail, diodes from equivalent sites on three separate wafers can be produced whose average current in forward bias is within 1 % while the total in-wafer standard deviation of current at the same fixed bias (0.5 V) is 6 %, dominated by a systematic cross-wafer variation that is described. This level of reproducibility now enables these devices to be used in pick-and-place systems for the manufacture of low-cost hybrid integrated microwave circuits.
