GaN‐based quasi‐vertical PIN diodes are grown on insulating sapphire substrates, and thus both the n‐electrode and the p‐electrode are made on the same side, which causes lateral current injection scheme. Therefore, one of the challenges for this design lies in the serious current crowding at the mesa edges, which leads to the local hole accumulation, and thus the Auger recombination significantly gives rise to the poor conductivity modulation in the drift region when the devices are forwardly biased. Herein, utilizing an embedded PN–GaN junction is proposed, such that the embedded PN–GaN junction is reversely biased when the PIN diode is in the on‐state condition. The built‐in electric field in the reversely biased PN–GaN junction depletes holes at the mesa edges, and correspondingly the Auger recombination can be decreased. The results also show that the proposed structures do not affect the breakdown voltage for PIN diodes.
In this article, we propose and investigate a GaN-based trench metal–insulator–semiconductor barrier Schottky rectifier with a beveled mesa and field plate (BM-TMBS). According to our study, the beveled mesa and field plate structures help to reduce the density of potential lines at the mesa corner and deplete the drift region in two-dimensional mode, respectively. By doing so, the electric field at the bottom corner of the trenches and Schottky contact/GaN interface can be decreased significantly and the breakdown voltage can also be improved remarkably when compared with the conventional TMBS rectifiers and the planar Schottky barrier diodes. Meanwhile, assisted by the beveled mesa structure, the improved current spreading effect and a better conductivity modulation can be obtained in the forward-conduction state. Our studies also show that the electric field profiles and charge-coupling effect can be influenced by the mesa angle, the insulating layer thickness (Tox), and the trench depth (Dtr). As a result, the optimized BM-TMBS rectifiers can obtain a high BV of ∼2 kV and a current density of ∼3 kA/cm2 at the forward bias of 2 V.
This study proposes to increase the breakdown voltage for GaN‐based PIN diodes using the polarization effect, such that a thin AlGaN layer is inserted into the drift layer to modulate the electric field profiles, and by properly designing the device architecture, the electric field in the drift layer can be remarkably reduced by the polarization effect, and this enables the enhancement of the breakdown voltage. The study further investigates the parametric sensitivity of the breakdown voltage for the proposed GaN‐based PIN diodes to different device structures with various drift layer thicknesses. Moreover, it is found that the position of the inserted AlGaN thin layer is also important in affecting the breakdown voltage, such that the AlGaN insertion layer reduces the electric field with the maximum intensity in the drift layer.
In this work, a hybrid trench MOS barrier Schottky diode (TMBS) structure is proposed to improve both the forward current density and the breakdown voltage (BV) by using TCAD simulation tools. The hybrid structure means that the conventional TMBS rectifier is combined with a p-NiO/n-GaN diode. This can modulate the lateral energy bands by removing the conduction band barriers for electrons. Thus, the improved current spreading effect and the better conductivity modulation can be obtained, leading to the increased current density. Meanwhile, the embedded p-type NiO layer can also help to reduce the electric field at Schottky contact interface and the edge of anode contact/p-NiO layer interface. Thus, the breakdown voltage can be improved remarkably. Moreover, a detailed optimization strategy for the hybrid TMBS is also analyzed by varying the p-NiO layer thickness (TNiO) and the lengths of the anode electrode that is covered on the p-NiO layer (LA).
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