Electronic Properties of GaN (0001) – Dielectric Interfaces

Abstract

The characteristics of clean n-and p-type GaN (0001) surfaces and the interface between this surface and Si0 2 , Si 3 N 4 , and Hf0 2 have been investigated. Layers of Si0 2 , Si 3 N 4 , or Hf0 2 were carefully deposited to limit the reaction between the film and clean GaN surfaces. After stepwise deposition, the electronic states were measured with x-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A valence band offset (VBO) of 2.0 ± 0.2 eV with a conduction band offset (CBO) of 3.6 ± 0.2 eV was determined for the GaN/Si0 2 interface. The large band offsets suggest Si0 2 is an excellent candidate for passivation of GaN. For the GaN/Si 3 N 4 interface, type II band alignment was observed with a VBO of -0.5 ± 0.2 eV and a CBO of 2.4 ± 0.2 eV. While Si 3 N 4 should passivate n-type GaN surfaces, it may not be appropriate for p-type GaN surfaces. A VBO of 0.3 ± 0.2 eV with a CBO of 2.1 ± 0.2 eV was determined for the annealed GaN/Hf0 2 interface. An instability was observed in the Hf0 2 film, with energy bands shifting -0.4 eV during a 650 °C densification anneal. The electron affinity measurements via UPS were 3.0, 1.1, 1.8, and 2.9 ±0.1 eV for GaN, Si0 2 , Si 3 N 4 , and Hf0 2 surfaces, respectively. The deduced band alignments were compared to the predictions of the electron affinity model and deviations were attributed to a change of the interface dipole. Interface dipoles contributed 1.6, 1.1 and 2.0 ± 0.2 eV to the band alignment of the GaN/Si0 2 , GaN/Si 3 N 4 , and GaN/Hf0 2 interfaces, respectively. It was noted that the existence of Ga-0 bonding at the heterojunction could significantly affect the interface dipole, and consequently the band alignment in relation to the GaN.

Illumination effects on electrical characteristics of GaN/AlGaN/GaN heterostructures and heterostructure field effect transistors and their elimination by proper surface passivation

“…The validity of this comparison depends on how much the metal changes the surface potential of the passivation. According to the calculations reported by Cook et al, 21 the Fermi level of Si 3 N 4 deposited on GaN is 5.6 eV below the vacuum level, which is close to the 5.1 eV work function of Nickel. 22 Hence, the band alignment of the two cases is roughly comparable and the charge extracted by integrating the C(V) is comparable to the charge in the non-metalized material.…”

GaN quantum-dots integrated in the gate dielectric of metal-oxide-semiconductor structures for charge-storage applications

“…In such a case, the Ga and the O atomic layers become, respectively, more positive and negative, and thereby, the resulting interface dipoles are expected to significantly increase the oxide levels with respect to GaN electronic levels. 9 In order to enlighten the electron injection/trapping process that constitutes the programming operation, the incremental-step-pulse programming (ISPP) method 16 was employed, i.e., programming (positive) voltage pulses, V G , with constant increasing step height (DV G ) were applied successively and the V FB was measured between two successive pulses. The pulse width t PULSE and voltage step were 10 ms and 1 V, respectively.…”