Interface trap states in Al₂O₃/AlGaN/GaN structure induced by inductively coupled plasma etching of AlGaN surfaces

Abstract

We have investigated the effects of the inductively coupled plasma (ICP) etching of AlGaN surface on the resulting interface properties of the Al 2 O 3 /AlGaN/GaN structures. The experimentally measured capacitancevoltage (C-V) characteristics were compared with those calculated taking into account the interface states density at the Al 2 O 3 /AlGaN interface. As a complementary method, photoassisted C-V method utilizing photons with energies less than the bandgap of GaN was also used to probe the interface state density located near AlGaN midgap. It was found that the ICP etching of the AlGaN surface significantly increased the interface state density at the Al 2 O 3 /AlGaN interface. It is likely that ICP etching induced the interface roughness, disorder of chemical bonds and formation of various type of defect complexes including nitrogen-vacancy-related defects at the AlGaN surface, leading to poor C-V curve due to higher interface state density at the Al 2 O 3 /AlGaN interface.

Characterization of capture cross sections of interface states in dielectric/III-nitride heterojunction structures

“…16,24,29 However as shown in Fig. 9, the values of capture cross section remained similar among these samples.…”

“…2 sample exhibited the higher interface state density probably due to interface disorder. 16,24,29 The ᭝V th in C-V characteristics was measured in the following manner. The measurement steps and the corresponding band diagrams are schematically shown in Figs.…”

On the origin of interface states at oxide/III-nitride heterojunction interfaces

“…1, we present a scheme of the studied MISH structures, i.e. : The investigated heterostructures were passivated using the two-step process: [24][25][26][27][28] (1) covered by a SiN (10 nm) protection film deposited by electron cyclotron resonance chemical vapor deposition (ECR CVD) to avoid damages of semiconductor surfaces during ohmic contact annealing and (2) after removal of the SiN film, covered with an Al 2 O 3 layer (20 nm) deposited by atomic layer deposition (ALD)…”

Characteristics of atomic layer deposited Gd2O3 on n-GaN with an AlN layer

“…Yatabe et al also showed in Al 2 O 3 / AlGaN/GaN structure that the C-V curves in the depletion region are stretched out more signicantly to the positive direction when the interface state density peaked at E C -0.1 eV is higher. 42 Signicant stretch out to the positive direction and high interface state density in the range of 0.1-0.2 eV observed for the sample with an AlN/Gd 2 O 3 bilayer, thus, can be associated with the nitrogen vacancy-related defects. Meanwhile, Freedsman et al showed in AlN/AlGaN/GaN MIS diodes that the trap density due to the AlN and AlGaN layers were located at 0.4-0.52 and 0.32-0.34 eV, respectively.…”