Direct evidence of Mg diffusion through threading mixed dislocations in GaN p–n diodes and its effect on reverse leakage current

Abstract

Mg diffusion is a common problem in GaN devices with p–n junctions. Although this impurity diffusion is reported to occur through threading dislocations (TDs), no direct evidence has yet been obtained. Therefore, we tried the direct observation of Mg diffusion by atom probe tomography (APT) analysis. The n-type drift layer of the fabricated p–n diode was exposed, and etch pits were formed on the drift layer to identify the TD position. The APT analysis around TDs was carried out by lifting out the drift layer around specific etch pits using a focused ion beam to include TDs. The relationship between the etch pit shape and the TD type was confirmed by cross-sectional scanning transmission electron microscopy observation. The APT analysis of two types of etch pits formed on the mixed dislocations was performed, and Mg diffusion was clearly observed through the mixed dislocations. In this work, we show direct evidence of Mg diffusion via mixed dislocations in GaN p–n diodes and its effect on reverse leakage current.

The influence of point defects on AlGaN-based deep ultraviolet LEDs

“…The activation energy of the trap H1 is ~0.1eV, which is consistent with the activation energy of Mg-related acceptors [32], such as MgAl [34] or MgGa [35]. The appearance of the threading dislocations through the whole quantum well after stress may cause the Mg diffusion along the dislocation line [36], which leads to the Mg-related acceptor traps, such as the deep level H1.…”

“…resulting in the Mg diffusion along the dislocation line and cause some Mg-related acceptor traps [36], degrade the AlGaN-based LEDs [50].…”

Improving Transport Properties of GaN-Based HEMT on Si (111) by Controlling SiH4 Flow Rate of the SiNx Nano-Mask

“…Similarly, this effect was also observed in the Mg-doped GaN film. The segregated Mg propagates through TDs and incorporates at the boundaries of pyramidal inversion domains (PIDs) to form an Mg-rich area, degrading device performance [42][43][44]. Up to now, the Si diffusion originated from the SiN x nano-mask, and how it involves in the 2DEG characteristics as well as GaN-based HEMT device performance have not been clearly understood yet, and needs to be explored further.…”

High Hole Concentration and Diffusion Suppression of Heavily Mg-Doped p-GaN for Application in Enhanced-Mode GaN HEMT

“…CL measurements revealed Mg diffusion along the dislocation [ 20 ]. Mg diffusion along the edge-type and mixed-type dislocations was also evidenced by transmission electron microscopy and atom probe tomography [ 21 , 22 ]. As a result, it is crucial to explore how to suppress Mg diffusion for better device performance of Mg-doped p-GaN/AlGaN/GaN HEMTs.…”