Impact of postdeposition annealing upon film properties of atomic layer deposition-grown Al2O3 on GaN

Abstract

Atomic layer deposition-grown Al2O3 thin films are grown on n-type GaN and annealed at 300 or 500 °C in various atmospheres. Metal–insulator–semiconductor capacitors (MISCAPs) are used as simplified test structures for AlGaN/GaN heterostructure field effect transistors with an Al2O3 gate dielectric. Electrical characterization of the unannealed MISCAPs reveals a low leakage current density of ∼1.4 × 10−9 A/cm2 at −2 MV/cm. Annealing at 500 °C in N2 or a forming gas results in a degradation of this leakage level by more than one order of magnitude, whereas the leakage current of the Al2O3 films annealed at 500 °C in O2 is increased to ∼5.2 × 10−9 A/cm2 at −2 MV/cm. The photoassisted capacitance–voltage technique, the conductance method, and border trap analysis are used to study the influence of the annealing ambient atmosphere upon the Al2O3/GaN interface. For all atmospheres, thermal treatments at 500 °C marginally affects the border oxide trap density, but the forming gas anneal at 500 °C passivates the interface traps most efficiently. While the O2 thermal treatment reduces the interface trap density in the Al2O3/GaN system, the N2 anneal creates interface trap states, indicating the formation of an oxygen deficient defect level at the Al2O3/GaN interface during N2 annealing.

Interface characterization of atomic layer deposited Al2O3 on m‐plane GaN

“…The dispersion of the C – V curves reflects oxide traps. However, in our study, the dispersion was very small, indicating a low density of oxide traps . Figure shows the frequency dependent C–V curves.…”

Analysis of threshold voltage instability in AlGaN/GaN MISHEMTs by forward gate voltage stress pulses

“…This charge density is higher than the 2DEG charge density in the bare AlGaN/GaN heterojunction (∼8 × 10 12 cm −2 ). According to the literature , the high‐ κ /III‐nitride interface can feature a relatively high density of defect states of ∼1 × 10 13 cm −2 . Driving the AlGaN/GaN system into the spill‐over region, transfers a high density of electrons to the oxide/GaN‐cap interface that can easily fill these interface states and bulk oxide traps close to the GaN interface.…”

Investigation of annealed, thin(∼2.6 nm)-Al2O3/AlGaN/GaN metal-insulator-semiconductor heterostructures on Si(111) via capacitance-voltage and current-voltage studies

“…Benefits of employing PDA have indeed been reported, including improving Al2O3 properties that leads to reduced oxide traps and threshold voltage hysteresis [15] as well as reducing average Dit at the Al2O3/GaN interface [16]. Yet some studies report adverse effects [17,18]. Page 3 of 28 AUTHOR SUBMITTED MANUSCRIPT -MRX-115333.R2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t Further systematic work is therefore needed for better understanding the impacts of PDA on ALD Al2O3 properties and then correlating these effects on AlGaN/GaN HEMT performance.…”