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The band alignments of two candidate dielectrics for ScAlN, namely, SiO 2 and Al 2 O 2 , were obtained by x-ray photoelectron spectroscopy. We compared the effect of deposition method on the valence band offsets of both sputtered and atomic layer deposition films of SiO 2 and Al 2 O 3 on Sc 0.27 Al 0.73 N (bandgap 5.1 eV) films. The band alignments are type I (straddled gap) for SiO 2 and type II (staggered gap) for Al 2 O 3 . The deposition methods make a large difference in relative valence band offsets, in the range 0.4–0.5 eV for both SiO 2 and Al 2 O 3 . The absolute valence band offsets were 2.1 or 2.6 eV for SiO 2 and 1.5 or 1.9 eV for Al 2 O 3 on ScAlN. Conduction band offsets derived from these valence band offsets, and the measured bandgaps were then in the range 1.0–1.1 eV for SiO 2 and 0.30–0.70 eV for Al 2 O 3 . These latter differences can be partially ascribed to changes in bandgap for the case of SiO 2 deposited by the two different methods, but not for Al 2 O 3 , where the bandgap as independent of deposition method. Since both dielectrics can be selectively removed from ScAlN, they are promising as gate dielectrics for transistor structures.
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Selective chemical vapor deposition of HfB 2 on Al 2 O 3 over SiO 2 and the acceleration of nucleation on SiO 2 by pretreatment with Hf[N(CH 3 ) 2 ] 4
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Valence band offsets for SiO 2 deposited by Atomic Layer Deposition on α -(Al x Ga 1-x ) 2 O 3 alloys with x = 0.26–0.74 were measured by X-ray Photoelectron Spectroscopy. The samples were grown with a continuous composition spread to enable investigations of the band alignment as a function of the alloy composition. From measurement of the core levels in the alloys, the bandgaps were determined to range from 5.8 eV (x = 0.26) to 7 eV (x = 0.74). These are consistent with previous measurements by transmission spectroscopy. The valence band offsets of SiO 2 with these alloys of different composition were, respectively, were −1.2 eV for x = 0.26, −0.2 eV for x = 0.42, 0.2 eV for x = 0.58 and 0.4 eV for x = 0.74. All of these band offsets are too low for most device applications. Given the bandgap of the SiO 2 was 8.7 eV, this led to conduction band offsets of 4.1 eV (x = 0.26) to 1.3 eV (x = 0.74). The band alignments were of the desired nested configuration for x > 0.5, but at lower Al contents the conduction band offsets were negative, with a staggered band alignment. This shows the challenge of finding appropriate dielectrics for this ultra-wide bandgap semiconductor system.more » « less
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Abstract High‐temperature, high‐velocity water vapor (steam‐jet) exposures were conducted on Y2O3, Y2SiO5, Y2Si2O7, and SiO2for 60 hours at 1400°C. Volatility of Y2O3was not observed. Phase‐pure Y2SiO5exhibited SiO2loss forming Y2O3and porosity. A mixed porous and dense Y2SiO5layer formed on the surface of Y2Si2O7due to SiO2depletion. The mechanisms and kinetics of the reaction between SiO2and H2O(g) to form Si(OH)4(g) from Y2SiO5, Y2Si2O7, and SiO2are discussed.more » « less
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The band alignment of Atomic Layer Deposited SiO 2 on (In x Ga 1−x ) 2 O 3 at varying indium concentrations is reported before and after annealing at 450 °C and 600 °C to simulate potential processing steps during device fabrication and to determine the thermal stability of MOS structures in high-temperature applications. At all indium concentrations studied, the valence band offsets (VBO) showed a nearly constant decrease as a result of 450 °C annealing. The decrease in VBO was −0.35 eV for (In 0.25 Ga 0.75 ) 2 O 3 , −0.45 eV for (In 0.42 Ga 0.58 ) 2 O 3 , −0.40 eV for (In 0.60 Ga 0.40 ) 2 O 3 , and −0.35 eV (In 0.74 Ga 0.26 ) 2 O 3 for 450 °C annealing. After annealing at 600 °C, the band alignment remained stable, with <0.1 eV changes for all structures examined, compared to the offsets after the 450 °C anneal. The band offset shifts after annealing are likely due to changes in bonding at the heterointerface. Even after annealing up to 600 °C, the band alignment remains type I (nested gap) for all indium compositions of (In x Ga 1−x ) 2 O 3 studied.more » « less
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1116/6.0000691
