Effect of anodic oxidation on the characteristics of lattice-matched AlInN/GaN heterostructures

The effect of anodic oxidation on the electronic characteristics of lattice-matched AlInN/GaN heterostructures was investigated using field-effect transistor (FET) structures with the gate areas in direct contact with the electrolytes. The gate surface of the FETs was subjected to anodic oxidation in 0.1 M KOH. The oxidized heterostructures were analyzed by electrochemical impedance spectroscopy and by modeling the characteristics of the electrolyte-gate FETs and the energy-band diagram of the heterostructures. This analysis suggested that the anodic treatment induced a bulk oxidation of the AlInN barrier. The Fermi level at the oxidized AlInN surface was shifted deep into the bandgap. The oxidation led to a reduction of the carrier mobility and to partial depletion of the channel

Combining diamond electrodes with GaN heterostructures for harsh environment ISFETs

Electrochemistry and biochemistry have always been ideal applications for diamond due to its chemical inertness and stability, sensitivity and biocompatibility. Several diamond ChemFET concepts have been proposed to date, however further improvements are still needed to obtain functional devices that can be operated efficiently beyond the reach of the well established silicon ISFET technology [P. Bergveld, Sensor and Actuators B. Chem. 88 (2003). pp. 1]. In this paper we describe a novel ISFET structure in which a boron doped diamond electrochemical gate electrode is combined and monolithically integrated with an InAlN/GaN HEMT structure. The new device merges the high chemical stability of diamond with the high transconductance and low pinch-off voltage of InAlN/GaN heterostructure FETs, resulting in a highly stable ISFET with high sensitivity. First devices have been fabricated and electrochemically characterized, expressing high current levels, a pH sensitivity of about 50 mV/pH, complete current modulation when operated within the electrochemical window of the electrode in the range of pH 1 to pH 13 and high stability upon pH cycling and the application of high anodic overpotentials. (C) 2009 Elsevier B.V. All rights reserved