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Article Dans Une Revue Micromachines Année : 2020

Vertical leakage in GaN-on-Si stacks investigated by a buffer decomposition experiment

Roland Püsche
  • Fonction : Auteur
Joff Derluyn
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  • PersonId : 1093160
Stefan Degroote
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  • PersonId : 1093161
Marianne Germain
  • Fonction : Auteur

Résumé

We investigated the origin of vertical leakage and breakdown in GaN-on-Si epitaxial structures. In order to understand the role of the nucleation layer, AlGaN buffer, and C-doped GaN, we designed a sequential growth experiment. Specifically, we analyzed three different structures grown on silicon substrates: AlN/Si, AlGaN/AlN/Si, C:GaN/AlGaN/AlN/Si. The results demonstrate that: (i) the AlN layer grown on silicon has a breakdown field of 3.25 MV/cm, which further decreases with temperature. This value is much lower than that of highly-crystalline AlN, and the difference can be ascribed to the high density of vertical leakage paths like V-pits or threading dislocations. (ii) the AlN/Si structures show negative charge trapping, due to the injection of electrons from silicon to deep traps in AlN. (iii) adding AlGaN on top of AlN significantly reduces the defect density, thus resulting in a more uniform sample-to-sample leakage. (iv) a substantial increase in breakdown voltage is obtained only in the C:GaN/AlGaN/AlN/Si structure, that allows it to reach V BD > 800 V. (v) remarkably, during a vertical I-V sweep, the C:GaN/AlGaN/AlN/Si stack shows evidence for positive charge trapping. Holes from C:GaN are trapped at the GaN/AlGaN interface, thus bringing a positive charge storage in the buffer. For the first time, the results summarized in this paper clarify the contribution of each buffer layer to vertical leakage and breakdown.
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Dates et versions

hal-03028138 , version 1 (01-12-2020)

Identifiants

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Alaleh Tajalli, Matteo Borga, Matteo Meneghini, Carlo de Santi, Davide Benazzi, et al.. Vertical leakage in GaN-on-Si stacks investigated by a buffer decomposition experiment. Micromachines, 2020, 11 (1), 101, 9 p. ⟨10.3390/mi11010101⟩. ⟨hal-03028138⟩
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