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Effect of Buffer Layer Design on Vertical GaN-on-GaN p-n and Schottky Power Diodes | IEEE Journals & Magazine | IEEE Xplore

Effect of Buffer Layer Design on Vertical GaN-on-GaN p-n and Schottky Power Diodes


Abstract:

We study verticalGaN p-n and Schottky power diodes with different buffer layer thicknesses grown on free-standingGaN substrates, using metalorganic chemical vapor deposit...Show More

Abstract:

We study verticalGaN p-n and Schottky power diodes with different buffer layer thicknesses grown on free-standingGaN substrates, using metalorganic chemical vapor deposition. High breakdown voltage of > 1 kV and low specific on-resistance of 3 \text{m}\Omega \cdot cm ^{2} are achieved on GaN p-n diode with 1~\mu \text{m} buffer layer and 9~\mu \text{m} drift layer without passivation or field plate. Detailed device analysis on GaN Schottky diodes indicates that buffer layer has significant impacts on the electrical properties of drift layer and thus device performances of GaN p-n diodes. A thicker buffer layer will significantly enhance the breakdown voltages of these devices, which is possibly due to the improved material quality of drift layers with reduced defect densities. Higher doping concentration in drift layer with thicker buffer layer will, however, lower breakdown voltage. More discussions reveal improving the material quality of drift layer plays amore dominant role in achieving high breakdown GaN-on-GaN p-n and Schottky diodes with increasing buffer layer thickness.
Published in: IEEE Electron Device Letters ( Volume: 38, Issue: 6, June 2017)
Page(s): 763 - 766
Date of Publication: 04 April 2017

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I. Introduction

Wurtzite III-nitride semiconductors have enabled a variety of applications including laser diodes (LDs) [1], light-emitting diodes (LEDs) [2]–[6], solar cells [7], photodetectors [8], [9] and high electron mobility transistors (HEMTs) [10]. Due to the advantages of low loss, low noise and low junction capacitance [11], GaN-based power diodes such as Schottky diodes and p-n diodes are also attractive for high power and high voltage applications. Conventional GaN power devices grown on foreign substrates such as Si and SiC, however, suffered from high defect densities (> 109 cm in the materials, which significantly limit device performances [12], [13]. Recently, vertical GaN p-n power diodes grown on low defect density (< 106 cm bulk GaN substrates have been demonstrated with promising performances such as high breakdown voltages and low on-resistance [14]–[18], where various device structures such as thicker drift layer, passivation and field plate have been proposed to further enhance the breakdown voltage of GaN p-n diodes. In addition to device structures, material properties such as defect density and doping concentration of device epilayers will also play a significant role in the performances of GaN p-n diodes. However, there are very few reports on this subject. In this work, we study the effect of buffer layer on the electrical properties of vertical GaN-on-GaN p-n and Schottky diodes.

References

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