Design and control of interface reaction between Al-based dielectrics and AlGaN layer in AlGaN/GaN metal-oxide-semiconductor structures

Abstract

Important clues for achieving well-behaved AlGaN/GaN metal-oxide-semiconductor (MOS) devices with Al-based gate dielectrics were systematically investigated on the basis of electrical and physical characterizations. We found that low-temperature deposition of alumina insulators on AlGaN surfaces is crucial to improve the interface quality, thermal stability, and variability of MOS devices by suppressing Ga diffusion into the gate oxides. Moreover, aluminum oxynitride grown in a reactive nitric atmosphere was proven to expand the optimal process window that would improve the interface quality and to enhance immunity against charge injection into the gate dielectrics. The results constitute common guidelines for achieving high-performance and reliable AlGaN/GaN MOS devices.

Control of Ga-oxide interlayer growth and Ga diffusion in SiO2/GaN stacks for high-quality GaN-based metal–oxide–semiconductor devices with improved gate dielectric reliability

“…Judging from the energy bandgap and conduction band offset between the insulators and the GaN-related materials, alumina (Al 2 O 3 ), SiO 2 , and their nitrides seem to be possible candidates for gate dielectrics. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Since the atomic layer deposition (ALD) technique for producing high-quality Al 2 O 3 was established, ALD-Al 2 O 3 films have been widely used for GaN-based MOS devices. 4,6,7,[10][11][12] However, regardless of the film deposition technique used, Al 2 O 3 involves an essential problem of electron trapping, 6,13,14) thus leading to significant I d -V g hysteresis and V th instability (positive V th shift).…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Since the atomic layer deposition (ALD) technique for producing high-quality Al 2 O 3 was established, ALD-Al 2 O 3 films have been widely used for GaN-based MOS devices. 4,6,7,[10][11][12] However, regardless of the film deposition technique used, Al 2 O 3 involves an essential problem of electron trapping, 6,13,14) thus leading to significant I d -V g hysteresis and V th instability (positive V th shift). Although electron trapping into Al 2 O 3 was proven to be suppressed by nitrogen incorporation into the oxide (Al-oxynitride: AlON), 13,14) the conduction band offset at the interface is still not high enough because of its moderate energy bandgap.…”

Vacancy-type defects in Al2O3/GaN structure probed by monoenergetic positron beams

“…positive charges fixed at the interface. 16,19,20 The V fb value increased as the annealing temperature increased, suggesting that the density of net positive charges decreased due to annealing up to 900 C. Under illumination, the value of V fb decreased, but the difference between the values measured with and without illumination decreased as the annealing temperature increased. We will come back to this point later.…”

“…[6][7][8][9] Thus, techniques for depositing oxide or nitride films on GaN and their electrical properties have been extensively studied. [10][11][12][13][14][15][16][17][18][19][20] Among many candidates, Al 2 O 3 prepared using atomic layer deposition (ALD) is seen as an attractive candidate for GaN-based MOS devices because of its high conduction-band offset on GaN, high dielectric constant, and high breakdown field.…”

Annealing behavior of open spaces in AlON films studied by monoenergetic positron beams

“…Details on the deposition conditions are given elsewhere. 5,9 AlON x and Al 2 O 3 depositions were performed in N 2 /O 2 and Ar/O 2 gas mixtures, respectively. The AlON x films with different nitrogen contents were prepared by controlling O 2 partial pressure during the deposition.…”