Sputtered AlN encapsulant for high-temperature annealing of GaN

Abstract

Reactively sputtered AlN is shown by electrical characterization of Pt/Au Schottky diodes to be an effect encapsulant for GaN annealed at 1100 °C. Schottky diodes formed on GaN encapsulated with AlN during the anneal had low reverse leakage currents with breakdown voltages in excess of 40 V. In contrast, samples annealed without the AlN layer had 3–4 orders-of-magnitude higher reverse leakage currents. Atomic force microscopy images of as-grown and annealed samples also demonstrate an increase in surface roughness and a change in morphology of the uncapped samples following annealing. Auger electron spectroscopy supports the hypothesis that the AlN encapsulant is reducing N loss from the GaN substrate. N loss in the uncapped samples is expected to create an n+-region at the surface that accounts for the high reverse leakage current and improved Ohmic behavior for the uncapped samples. The use of AlN encapsulation will enable the realization of all ion implanted GaN metal semiconductor field effect transistors.

Wet chemical etching survey of III-nitrides

“….= AINwasreactively sputter deposited on aSi substrate to a thickness of-1200~using aN2 discharge and a pure Al target. This type of AIN film was shown to be an effective annealing cap for GaN at a temperature of 1100"C [34].…”

Implantation activation annealing of Si-implanted gallium nitride at temperatures > 1,100 C

“…The first set of samples was encapsulated with 120 nm of sputter deposited AlN (11). The AlN was deposited in an Ar-plasma at 300 W using an Al-target and a 10 sccm flow of N,.…”

Surface Acoustic Wave Devices for Harsh Environment

“…It has demonstrated to be an ideal candidate for packaging SiC-devices for high-temperature applications [5] thanks to its CTE that closely matches those of Si (3.5 x 10 -6 °C -1 ) and SiC (3.7 x 10 -6 °C -1 ), high electrical resistivity, high mechanical strength, and chemical inertness. Reactively sputtered AlN films have been used as an effective encapsulant for GaN [6] at an annealing temperature of 1100°C substituting the standard dielectric encapsulants, such as SiO 2 and Si 3 N 4 , that are not viable at so high temperatures. AlN maintains its piezoelectricity up to 1200°C in vacuum and shows very high BAW and SAW velocities (∼6000 m/s and 11300 m/s for transversal and longitudinal BAWs propagating along the z direction, 5607 m/s for SAWs propagating in the z plane) that make it the ideal candidate for microwave electroacoustic devices implementation.…”