Passivation of Surface and Interface States in AlGaN/GaN HEMT Structures by Annealing

Abstract

The Ni/AlGaN interfaces in AlGaN/GaN Schottky diodes were investigated to explore the physical origin of post-annealing effects using electron beam induced current (EBIC), current-voltage (I-V) characteristics, and X-ray photoelectron spectroscopy (XPS). The EBIC images of the annealed diodes showed that the post-annealing process reduces electrically active states at the Schottky metal/AlGaN interfaces, leading to improvement of diode performance, for example a decrease in reverse leakage current and an increase in Schottky barrier heights. Pulsed I-V characteristics indicate the Fermi level is up-shifted after annealing, resulting in a larger sheet carrier density at the AlGaN/GaN interface. Unintentional oxidation of the free AlGaN surface during the post-annealing process, revealed by XPS analysis, may prevent electron trapping near the drain-side of the gate edges. We suggest that the post-annealing process under an optimized conditions can be an effective way of passivating AlGaN/GaN heterojunction field-effect transistors.

Barrier height enhancement of Ni/GaN Schottky diode using Ru based passivation scheme

“…8 There have been many reports about the origin of surface states in GaN-based materials, for example threading dislocations (TDs), nitrogen vacancies (VN), and oxygen impurities. 5 The passivation of surface/ interface states remains an important problem for GaN based semiconductor devices. Different surface passivation schemes have been reported for the reduction of surface state density in GaN.…”

“…NH 4 OH, (NH 4 ) 2 S x , Na 2 S, chlorination, and Si 3 N 4 have been used for passivation by various groups. [5][6][7][8][9][10] The success of a passivating technique depends on choosing a species that has a lower heat of oxide formation than Ga 2 O 3 . 11 So the chemical species should be strongly chemisorbed occupying the active surface sites to prevent oxidation.…”

A Schottky-Type Metal-Semiconductor-Metal Al0.24Ga0.76N UV Sensor Prepared by Using Selective Annealing

“…Despite much progress, UV sensor technologies are still limited by high leakage current and poor UV-to-visible rejection ratio (UVRR) values, which are attributed to the low crystalline qualities of the ternary epitaxial layers and high defect densities. Rapid thermal annealing (RTA) is recognized as one of the methods to overcome these limitations because it improves device performance metrics that include trap density, device uniformity, and contact behavior [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ].…”

High performance TiN gate contact on AlGaN/GaN transistor using a mechanically strain induced P-doping

“…4,5 A post-annealing is commonly performed to improve contact reliability. [6][7][8] On the other hand, to form ohmic contacts on N-type III-Nitrides semiconductors, a titanium (Ti) layer is usually deposited by evaporation. After annealing at high temperature, a TiN layer is obtained on top of a complex structure based on metallic aggregates.…”