Influence of carbon impurities and oxygen vacancies in Al2O3 film on Al2O3/GaN MOS capacitor characteristics

Mutsunori Uenuma,Yukiharu Uraoka,Yuta Fujimoto,Yuta Tominaga,Sho Sonehara,Kiyoshi Takahashi,Yasuaki Ishikawa

doi:10.1063/1.5041501

Abstract

Effects of carbon impurities and oxygen vacancies in Al2O3 film on the characteristics of Al2O3/GaN MOS capacitors were studied using the different atomic layer deposition (ALD) precursor and high-pressure water vapor annealing (HPWVA). Trimethyl aluminum (TMA: Al(CH3)3) and dimethyl aluminum hydride (DMAH: Al(CH3)2H) were used as ALD precursors to control the carbon impurities. On the other hand, oxygen vacancies in Al2O3 film were suppressed using the HPWVA. The DMAH precursor reduced the concentration of carbon impurities in the ALD Al2O3 film. It was found that the interface trap density (Dit) was mainly affected by the carbon impurities rather than the oxygen vacancies at the Al2O3/GaN interface. On the other hand, voltage stress induced flat band voltage (VFB) shift was attributed to both the carbon impurities and the oxygen vacancies.

Highlights

Gallium nitride (GaN) power device have been widely investigated due to their high electrical performances
The Al2O3 gate insulator are typically obtained by atomic layer deposition (ALD) using trimethyl aluminum (TMA: Al(CH3)3) as aluminum precursor
It has been observed that the Dit and VFB are strongly affected by the carbon impurities at the interface of the Al2O3/GaN structure

Summary

Introduction

Gallium nitride (GaN) power device have been widely investigated due to their high electrical performances. In the GaN metal-oxide-semiconductor field-effect transistor (MOSFET), high quality insulator and insulator/GaN interface are important to prevent charge traps and fixed charges caused by the degradation of the device performance. Pre-treatment of the substrate,[1,2,3] fabrication conditions,[4] and post-deposition annealing[5] play important roles in the manufacturing process. Al2O3 is of interest as a gate insulator for high-power GaN semiconductor transistors.[5,6] The Al2O3 gate insulator are typically obtained by atomic layer deposition (ALD) using trimethyl aluminum (TMA: Al(CH3)3) as aluminum precursor. The Al2O3 film has various charge traps and fixed charges. The trap defects consists mainly due to carbon impurities and unsatisfied chemical bonds such as oxygen vacancies

Methods

Results

Conclusion