Low interface trapped charge density in MBEin situgrown Si₃N₄cubic GaN MIS structures

Abstract

In this work we report on the electrical characterization of nonpolar cubic GaN metal-insulator-semiconductor (MIS) structures. Si 3 N 4 layers were deposited in situ on top of cubic GaN grown on 3C-SiC (0 0 1) substrates. The electric characteristics of the MIS structures are determined by current-voltage measurements and by capacitance and admittance spectroscopy techniques. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) was used to investigate the composition of our samples. From the flat band voltage in the MIS capacitors and a detailed band diagram analysis, the conduction band discontinuity of Si 3 N 4 and cubic GaN was evaluated 1.17 eV, which is slightly lower than reported for hexagonal GaN. By admittance spectroscopy interface state densities are calculated. Current-voltage characteristics were used to evaluate the influence of the substrate temperature on the insulating properties of the MIS structures. The energetic position of the interface traps was found to be about 0.3 eV below the conduction band of cubic GaN. The density of these traps is 2.5 × 10 11 cm −2 eV −1 . We find a conductivity minimum in the MIS structure grown at 600 • C.

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