Influence of Ni Schottky contact area on two-dimensional electron-gas sheet carrier concentration of strained AlGaN∕GaN heterostructures

Abstract

The influence of Ni Schottky contact area on two-dimensional electron-gas (2DEG) sheet carrier concentration of strained AlGaN∕GaN heterostructures has been investigated by depositing different areas of Ni Schottky contact on the structure. With the measured capacitance-voltage (C-V) curves, the 2DEG sheet carrier concentrations with different Ni Schottky contact areas were calculated. It is shown that with the increased area of Ni Schottky contact on strained AlGaN∕GaN heterostructures, the 2DEG sheet carrier concentration is decreased, and when the area of Ni Schottky contact is increased to some extent, the decreased 2DEG sheet carrier concentration tends to be constant. A hypothetic model of the interaction among the electrons of Ni Schottky metal, the surface donor states of AlGaN barrier layer, and 2DEG electrons in strained AlGaN∕GaN heterostructures is proposed to explain the above results. The current-voltage (I-V) characteristics for the different areas of Ni Schottky contact confirm the results obtained by C-V characteristics.