The Effect of Heavy Fe-Doping on 3D Growth Mode and Fe Diffusion in GaN for High Power HEMT Application.

Jin-Ji Dai,Cheng-Wei Liu,Hsin-I Hsiao,Shao-Chien Chang,Thi Thu Mai,Ssu-Kuan Wu,Hua-Chiang Wen,Luc Huy Hoang,Umeshwar Reddy Nallasani,Chieh-Piao Wang,Wu-Ching Chou

doi:10.3390/ma15062058

Jin-Ji Dai, Cheng-Wei Liu + Show 9 more

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https://doi.org/10.3390/ma15062058

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Abstract

The high electron mobility transistor (HEMT) structures on Si (111) substrates were fabricated with heavily Fe-doped GaN buffer layers by metalorganic chemical vapor deposition (MOCVD). The heavy Fe concentrations employed for the purpose of highly insulating buffer resulted in Fe segregation and 3D island growth, which played the role of a nano-mask. The in situ reflectance measurements revealed a transition from 2D to 3D growth mode during the growth of a heavily Fe-doped GaN:Fe layer. The 3D growth mode of Fe nano-mask can effectively annihilate edge-type threading dislocations and improve transfer properties in the channel layer, and consequently decrease the vertical leakage current by one order of magnitude for the applied voltage of 1000 V. Moreover, the employment of GaN:C film on GaN:Fe buffer can further reduce the buffer leakage-current and effectively suppress Fe diffusion.

Highlights

GaN-based high electron mobility transistors (HEMTs) on Si substrate have received tremendous attention in recent years due to their high breakdown field, high saturation velocity, and low cost in the application of high-voltage and high-frequency devices [1,2].achieving high breakdown voltage (VBD ) and low dynamic on-resistance (RON )for the GaN HEMTs remains a challenge [1,3]
The effect of p-type Fe nano-mask on 3D island growth was studied for the application in high power GaN HEMT
The SEM image verified that Fe segregation generates a growth mask to initiate a 3D growth mode in the GaN:Fe buffer layer

Summary

Introduction

GaN-based high electron mobility transistors (HEMTs) on Si substrate have received tremendous attention in recent years due to their high breakdown field, high saturation velocity, and low cost in the application of high-voltage and high-frequency devices [1,2].achieving high breakdown voltage (VBD ) and low dynamic on-resistance (RON )for the GaN HEMTs remains a challenge [1,3]. A highly insulating buffer with good crystalline quality is required to suppress the leakage current for the GaN-on-Si HEMTs operating at high voltage. The un-doped GaN (u-GaN) on Si structures typically exhibits n-type conductivity due to the existence of intrinsic defects, such as high threading dislocation (TD) densities of about 109 –1010 cm−2 resulted from the lattice and thermal expansion mismatch, nitrogen vacancies (VN ), residual silicon and oxygen impurities [4]. A comprehensive study to mitigate buffer TD densities and compensate n-type defects is highly essential. The purpose of this work is to develop three-dimensional (3D) growth techniques and acceptor doping to reduce TD densities and compensate the intrinsic n-type defects, respectively

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