Highly reproducible fabrication of back-gated GaAsAlGaAs heterostructures using AuGeNi ohmic contacts with initial Ni layer

We show for back-gated GaAs Alx Ga1-x As heterostructures that a thin Ni layer deposited prior to the standard AuGeNi Ohmic contacts dramatically improves the device yield by keeping the annealed contacts from reaching the back gate 1.2 μm below the channel. A systematic investigation of the contact resistance and the back-gate characteristics as a function of the initial Ni layer thickness and the annealing temperature demonstrates that back-gated structures with contact resistance below 100 can be obtained with a high yield of 90%.