AlGaN/GaN MOSHFETs with HfO2 gate oxide: A simulation study

Hayashi, Yuya; Sugiura, S.; Kishimoto, Shigeru; Mizutani, Takashi

doi:10.1016/j.sse.2010.03.022

Cited by 16 publications

(13 citation statements)

References 24 publications

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“…24 Therefore, from hypothesis A it follows that one should expect an increase of Q f vs. x, which is in contradiction with our observation. Another hypothesis, introduced by Hayashi et al 25 and Tapajna and Kuzmik 23 (hypothesis B) suggests that Q f is linked to the ionized donor-like surface defects formed during the growth on the III-N heterostructure. Furthermore, it was shown by Gordon et al 26 that the concentration of donor-like surface defects increases with increasing x; thus within hypothesis B, one should also observe, contrary to our results, an enlargement of Q f vs. x.…”

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confidence: 99%

Origin of positive fixed charge at insulator/AlGaN interfaces and its control by AlGaN composition

Matys

Stoklas

Blaho

et al. 2017

Applied Physics Letters

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The key feature for the precise tuning of Vth in GaN-based metal-insulator-semiconductor (MIS) high electron mobility transistors is the control of the positive fixed charge (Qf) at the insulator/III-N interfaces, whose amount is often comparable to the negative surface polarization charge (Qpol−). In order to clarify the origin of Qf, we carried out a comprehensive capacitance-voltage (C-V) characterization of SiO2/AlxGa1–xN/GaN and SiN/AlxGa1–xN/GaN structures with Al composition (x) varying from 0.15 to 0.4. For both types of structures, we observed a significant Vth shift in C-V curves towards the positive gate voltage with increasing x. On the contrary, the Schottky gate structures exhibited Vth shift towards the more negative biases. From the numerical simulations of C-V curves using the Poisson's equation supported by the analytical calculations of Vth, we showed that the Vth shift in the examined MIS structures is due to a significant decrease in the positive Qf with rising x. Finally, we examined this result with respect to various hypotheses developed in the literature to explain the origin of the positive Qf at insulator/III-N interfaces.

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mentioning

confidence: 99%

Origin of positive fixed charge at insulator/AlGaN interfaces and its control by AlGaN composition

Matys

Stoklas

Blaho

et al. 2017

Applied Physics Letters

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“…2. It is observed from the figure that the reason behind formation of positive interface charge in HfO 2 is due to presence of E F0 below E C N L [14], whereas in SiO 2 and Al 2 O 3 the presence of negative interface charges is due to position of E F0 above E C N L [6].…”

Section: Model Development For Electric Fieldmentioning

confidence: 90%

Modeling and simulation of oxide dependent 2DEG sheet charge density in AlGaN/GaN MOSHEMT

et al. 2015

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Oxide dielectric present in metal oxide semiconductor high electron mobility transistor plays an important role during formation of two dimensional electron gas (2DEG). The sheet charge concentration (n s ) is dependent on the Eigenenergy states present in triangular quantum well at AlGaN/GaN interface. The energy states are in fact functions of vertical electric field at the edge of the well. Therefore in this paper a model is developed to find out Electric field and flat-band voltage (V T ) by adopting energy band approach to incorporate oxide parameters in it unlike the conventional method of solving Poisson's equation, which is the uniqueness of this paper. The Eigenenergy states are dependent non-linearly on electric field. In the present case, three quantum states in the well are considered along with the Fermi-Dirac distribution function to obtain n s . The dependence of 2DEG density, electric field and flat-band voltage on the oxide parameters such as thickness and electrical permittivity is analyzed. With respect to thickness in SiO 2 and Al 2 O 3 , n s shows inverse relationship; whereas in HfO 2 it is direct due to positive charges accumulated at oxide/barrier interface. To the best of author's knowledge the work is first of its kind and due to lack of experimental data; the obtained results are compared with TCAD results to validate the model.

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“…Let us therefore discuss this issue first. To account for electrostatic inactivity of P S in the oxide/III-N structures, models assuming (i) ionized SDs formed on the III-N barrier surface side 11,31,32 (adopted here) related to, e.g., V N or (ii) oxide/III-N positive fixed charge related to the barrier oxidation (e.g., O substituting nitrogen site), 12,13 or (iii) III-N surface polarity inversion after Al 2 O 3 deposition have been proposed. 12 The latter model, however, would lead to a large difference in V th -t ox dependence for MOS-HEMTs with and without GaN cap (Q ef /q ¼ 1 Â 10 13 cm À2 and 4.5 Â 10 13 cm À2 , respectively) in contradiction to the data presented in Fig.…”

Section: Discussionmentioning

confidence: 99%

Impact of GaN cap on charges in Al2O3/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations

Ťapajna

Jurkovič

Valik

et al. 2014

Journal of Applied Physics

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Oxide/semiconductor interface trap density (Dit) and net charge of Al2O3/(GaN)/AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor (MOS-HEMT) structures with and without GaN cap were comparatively analyzed using comprehensive capacitance measurements and simulations. Dit distribution was determined in full band gap of the barrier using combination of three complementary capacitance techniques. A remarkably higher Dit (∼5–8 × 1012 eV−1 cm−2) was found at trap energies ranging from EC-0.5 to 1 eV for structure with GaN cap compared to that (Dit ∼ 2–3 × 1012 eV−1 cm−2) where the GaN cap was selectively etched away. Dit distributions were then used for simulation of capacitance-voltage characteristics. A good agreement between experimental and simulated capacitance-voltage characteristics affected by interface traps suggests (i) that very high Dit (>1013 eV−1 cm−2) close to the barrier conduction band edge hampers accumulation of free electron in the barrier layer and (ii) the higher Dit centered about EC-0.6 eV can solely account for the increased C-V hysteresis observed for MOS-HEMT structure with GaN cap. Analysis of the threshold voltage dependence on Al2O3 thickness for both MOS-HEMT structures suggests that (i) positive charge, which compensates the surface polarization, is not necessarily formed during the growth of III-N heterostructure, and (ii) its density is similar to the total surface polarization charge of the GaN/AlGaN barrier, rather than surface polarization of the top GaN layer only. Some constraints for the positive surface compensating charge are discussed.

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AlGaN/GaN MOSHFETs with HfO2 gate oxide: A simulation study

Cited by 16 publications

References 24 publications

Origin of positive fixed charge at insulator/AlGaN interfaces and its control by AlGaN composition

Origin of positive fixed charge at insulator/AlGaN interfaces and its control by AlGaN composition

Modeling and simulation of oxide dependent 2DEG sheet charge density in AlGaN/GaN MOSHEMT

Impact of GaN cap on charges in Al2O3/(GaN/)AlGaN/GaN metal-oxide-semiconductor heterostructures analyzed by means of capacitance measurements and simulations

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