FABRICATION AND CHARACTERIZATION OF DIRECT SCHOTTKY CONTACTS TO 2-DIMENSIONAL ELECTRON-GAS IN GAAS/ALGAAS QUANTUM-WELLS

Pt Schottky contacts to the edge of a two-dimensional electron gas in a GaAs/AlGaAs system have been manufactured using a newly developed in-situ etching and electroplating technology. The electroplating takes place selectively on the edge of the quantum well. It is shown that the in-situ etching prior to deposition leads to more uniform electroplating due to the removal of native oxides. I-V and C-V measurements have been made in order to compare the diodes with conventional Schottky diodes. It can be shown that the capacitance shows functionally the relationship predicted by theory, which demonstrates that we have manufactured a contact to a 2-dimensional electron gas. I-V measurements at low temperatures reveal parallel ohmic conductance. It is shown qualitatively that tunneling through the extremely thin barrier plays an important role in the current conduction, which explains the high ideality factor and the low apparent barrier height compared to bulk Schottky diodes.