Soft x-ray photoemission studies of Hf oxidation

Süzer, Şefik; Sayan, Şafak; Holl, Mark M. Banaszak; Garfunkel, Eric; Hussain, Zahid; Hamdan, Nasser M.

doi:10.1116/1.1525816

Cited by 105 publications

(61 citation statements)

References 14 publications

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“…This value was 13.7 eV for as-grown and annealed HfO 2 films, which was consistent with our previous study (13.6-13.7 eV) 13 (13.9 eV). 31 The same value of (E Hf4f7/2 -E V ) HfO2 was obtained for Ga-face GaN, which is not shown. Therefore, the value of (E Hf4f7/2 -E V ) HfO2 was determined to be 13.7 eV, which was used for the band offset calculation.…”

Section: Resultssupporting

confidence: 56%

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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The effects of surface pretreatment, dielectric growth, and post deposition annealing on interface electronic structure and polarization charge compensation of Ga-and N-face bulk GaN were investigated. The cleaning process consisted of an ex-situ wet chemical NH 4 OH treatment and an in-situ elevated temperature NH 3 plasma process to remove carbon contamination, reduce oxygen coverage, and potentially passivate N-vacancy related defects. After the cleaning process, carbon contamination decreased below the x-ray photoemission spectroscopy detection limit, and the oxygen coverage stabilized at $1 monolayer on both Ga-and N-face GaN. In addition, Ga-and N-face GaN had an upward band bending of 0.8 6 0.1 eV and 0.6 6 0.1 eV, respectively, which suggested the net charge of the surface states and polarization bound charge was similar on Ga-and N-face GaN. Furthermore, three dielectrics (HfO 2 , Al 2 O 3 , and SiO 2 ) were prepared by plasma-enhanced atomic layer deposition on Ga-or N-face GaN and annealed in N 2 ambient to investigate the effect of the polarization charge on the interface electronic structure and band offsets. The respective valence band offsets of HfO 2 , Al 2 O 3 , and SiO 2 with respect to Ga-and N-face GaN were 1.4 6 0.1, 2.0 6 0.1, and 3.2 6 0.1 eV, regardless of dielectric thickness. The corresponding conduction band offsets were 1.0 6 0.1, 1.3 6 0.1, and 2.3 6 0.1 eV, respectively. Experimental band offset results were consistent with theoretical calculations based on the charge neutrality level model. The trend of band offsets for dielectric/GaN interfaces was related to the band gap and/or the electronic part of the dielectric constant. The effect of polarization charge on band offset was apparently screened by the dielectric-GaN interface states. V C 2014 AIP Publishing LLC.

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Section: Resultssupporting

confidence: 56%

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Yang

Eller

Nemanich

2014

Journal of Applied Physics

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“…The Hf 4 f binding energies, at 18-21 eV binding energy, are substantially larger than those reported by Renault and coworkers [23], and Hf 4 f binding energies and the valence band edge are slightly larger than those reported elsewhere [24][25][26]. Indeed, with Gd doping, the Hf 4 f binding energies increase, as seen in Figure 2.…”

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confidence: 60%

The n-type Gd-doped HfO2 to silicon heterojunction diode

et al. 2007

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Gd-doped HfO 2 films were deposited on p-type silicon substrates in a reducing atmosphere. Photoemission measurements indicate the ntype character of Gd-doped HfO 2 due to overcompensation with oxygen vacancies. The Gd 4 f photoexcitation peak at 5.5 eV below the valence band max imum is identified using both resonant photoemission and first-principles calculations of the f hole. The rectifying (diode-like) properties of Gd-doped HfO 2 to silicon heterojunctions are demonstrated.PACS 68.55.Ln; 29.40.Wk; 81.05.Je ________________________________________ While HfO 2 has attracted considerable attention as a high-κ dielectric oxide [1][2][3][4], the gadolinium doping of a number of wide band gap semiconductors [5][6][7][8][9] suggests that Gd doping of HfO 2 may also lead to a dilute magnetic semiconduc tor [10,11]. Moreover, semiconducting Gd-doped HfO 2 may provide a promising new class of materials for neutron detec tion technologies.A gadolinium-based semiconductor diode might be better for neutron detection because of the large thermal neutron absorption cross section of gadolinium (on average ~ 46,000barns). The 157 Gd(n,γ)→ 158 Gd and 155 Gd(n,γ)→ 156 Gd reactions lead to the emission of low-energy gamma rays and conversion electrons, most of which are emit ted at energies below 220 eV [12][13][14][15]. The appeal of using 157 Gd is due to its large thermal neutron cross section of 240 000 barns [16,17]. Although sensitive to gamma radia tion, the big advantage of gadolinium over boron is not only the high neutron capture cross section but also that this cross section extends to higher neutron energies (200 meV)thanis the case for boron. While all-boron-carbide neutron detectors have been demonstrated [18][19][20], and their potential detection efficiency is much higher than that of many semiconductor materials (likely well above 50% for 10 B-enriched devices), the drawback to all boron-based devices is the need for a mod erator to reduce the neutron kinetic energies to 25-30 meV. Fissile radiation sources like 235 U or 239 Pu produce 1-2MeV neutrons, so the moderator must be significant.Since neutron capture by gadolinium leads to production of a conversion electron, the pulse height will be smaller than in the case of neutron capture by boron (10 4 charges versus 10 6 per neutron capture). Accordingly, it is advantageous to see if a Gd-doped HfO 2 diode can be fabricated that can be impedance matched and compatible with a high gain, low noise amplifier. A heterojunction diode with silicon would serve this purpose. Although Gd is expected to be a p-type dopant in HfO 2 , we attempted to fabricate a heterojunction diode of n-type Gd-doped HfO 2 with silicon by overcompen sating the Gd acceptor states by donor states introduced by oxygen vacancies, as such a device would likely have a larger depletion region and therefore larger detection volume.The Gd-doped (3 at. %) HfO 2 films were deposited on single crystal silicon (100) p-type substrates using pulsed laser deposition (PLD) at a growth rate of a...

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“…The Hf 4f binding energies of 18-21 eV are substantially larger than those reported by Renault et al; 20 Hf 4f binding energies and valence band edge are similar 6 or slightly larger than those reported elsewhere. [21][22][23] As seen in Fig. 2, the Hf 4f binding energies increase when Gd doping is increased from 3% to 10%.…”

mentioning

confidence: 78%

The electronic structure change with Gd doping of HfO2 on silicon

Losovyj

Ketsman

Sokolov

et al. 2007

Applied Physics Letters

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Gd-doped HfO2 films deposited on silicon substrates undergo a crystallographic change from monoclinic to fluorite (cubic) phase with increasing Gd concentrations. The crystallographic phase change is accompanied by a small increase in the valence bandwidth and in the apparent band offset in the surface region. Electrical measurements show pronounced rectification properties for lightly doped Gd:HfO2 films on p-Si and for heavily-doped Gd:HfO2 films on n-Si, suggesting a crossover from n-type to p-type behavior with increasing doping level.

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Soft x-ray photoemission studies of Hf oxidation

Cited by 105 publications

References 14 publications

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

Surface band bending and band alignment of plasma enhanced atomic layer deposited dielectrics on Ga- and N-face gallium nitride

The n-type Gd-doped HfO2 to silicon heterojunction diode

The electronic structure change with Gd doping of HfO2 on silicon

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