Effect of Si Doping on the Performance of GaN Schottky Barrier Ultraviolet Photodetector Grown on Si Substrate

Fangzhou Liang,Wen Chen,Hui Yang,Jianxun Liu,Meixin Feng,Yingnan Huang,Qibao Wu,Xiujian Sun,Qian Sun,Xiaoning Zhan

doi:10.3390/photonics8020028

Abstract

GaN Schottky barrier ultraviolet photodetectors with unintentionally doped GaN and lightly Si-doped n−-GaN absorption layers were successfully fabricated, respectively. The high-quality GaN films on the Si substrate both have a fairly low dislocation density and point defect concentration. More importantly, the effect of Si doping on the performance of the GaN-on-Si Schottky barrier ultraviolet photodetector was studied. It was found that light Si doping in the absorption layer can significantly increase the responsivity under reverse bias, which might be attributed to the persistent photoconductivity that originates from the lowering of the Schottky barrier height. In addition, the devices with unintentionally doped GaN demonstrated a relatively high-speed photo response. We briefly studied the mechanism of changes in Schottky barrier, dark current and the characteristic of response time.

Highlights

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GaN, with a natural direct bandgap of approximately 3.4 eV, has a very high absorption coefficient for ultraviolet (UV) light and has become an ideal semiconductor material used for UV detection [1,2]
GaN-based UV PDs are grown on a conventional sapphire substrate

Summary

Introduction

GaN, with a natural direct bandgap of approximately 3.4 eV, has a very high absorption coefficient for ultraviolet (UV) light and has become an ideal semiconductor material used for UV detection [1,2]. GaN-based UV photodetectors (PDs) have a small size and high efficiency and can be widely used in the civilian and military field, such as in biological sensing, flame monitoring and missile plume detection. GaN-based UV PDs are grown on a conventional sapphire substrate. Compared with a sapphire substrate, a Si substrate has a larger wafer size and lower material cost. Fabrication of GaN-based UV PDs on a Si substrate can both reduce the device cost and enhance the reliability, qualities which are becoming increasingly important nowadays

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