GaN Schottky Diode with TiW Electrodes on Silicon Substrate Based on AlN/AlGaN Buffer Layer

Sheng-Po Chang

doi:10.1155/2012/452310

Abstract

We report the fabrication of GaN Schottky photodiodes (PDs) on Si(111) substrates coated with an AlN/AlGaN buffer multilayer. It was found that their dark current was much smaller than that of identical devices prepared on sapphire substrates. With an incident wavelength of 359 nm, the maximum responsivity of the n−-GaN Schottky photodetectors with TiW contact electrodes was 0.1544 A/W, corresponding to a quantum efficiency of 53.4%. For a given bandwidth of 1 kHz and bias of 5 V, the resultant noise equivalent power (NEP) of n−-GaN Schottky photodetectors with TiW electrodes was1.033×10-12 W, corresponding to a detectivity (D*) of1.079×1012 cm-Hz0.5 W−1.

Highlights

There are numerous applications demanding the usage of ultraviolet (UV) photodetectors (PDs)
The small dark current was a clear benefit derived from the insertion of two additional stacks of buffer multilayers into the overall device structure
Compared with III-nitride PDs grown on a sapphire substrate [25, 26], the smaller peak responsivity observed from samples grown on Si substrates can be directly attributed to a highly defective epitaxial layer

Summary

Introduction

There are numerous applications demanding the usage of ultraviolet (UV) photodetectors (PDs). GaN has a wide direct band gap (Eg = 3.4 eV) and a high saturation velocity (vs = 2.7 × 107 cm/s) and is widely considered to be one of the most promising materials for realizing UV PDs [1,2,3,4,5,6,7,8,9,10,11,12,13] This material is remarkably tolerant of aggressive environments because of its thermal stability and radiation hardness. Growth of high-quality InGaN/GaN films on a silicon substrate was possible owing to prior deposition of an AlGaN buffer and two high-temperature (HT) AlN interlayers before attempting GaN growth This particular growth scheme effectively confined the threading dislocation to the vicinity of the interfacial layer in the AlGaN/HT-AlN buffer layers. Schottky photodiodes are discussed thereafter, along with their resultant optical and electrical properties

Experimental

Results and Discussion

V 4 V 3 V

V up to 5 V step 1 V

Summary