Optical Response Study of the Al/a-Sic:H Schottky Diode for Different Substrate Temperatures of the R.F. Sputtered a-Sic:H Thin Film

L Magafas

doi:10.1080/0882751021000010627

Abstract

In the present work, Schottky diodes of Al/a-SiC:H included in the structure Al/a-SiC:H/c-Si(n)/Al were fabricated and their optical response was studied in the wavelength region from 350 nm up to 1000 nm, for different substrate temperatures,Ts(from 30°C up to 290°C) of the r.f. sputtered a-SiC:H thin film. The spectral response of these structures exhibits two maximum values of quantum efficiency. The first maximum is presented at wavelengthλ≅525nm and the other atλ=850850 nm, which are attributed to the Aa-SiC:H Schottky junction and the a-SiC:H/c-Si(n) isotype heterojunction, respectively. The position of the first maximum owing to the Al/a-SiC:H junction as well as the values of quantum efficiency, for the range of wavelengths from 350 nm up to 700 nm, depends on the substrate temperature,Ts, of the a-SiC:H thin film. In the case thatTsis 120°C, the spectral response of the Al/a-SiC:H/c-Si(n)/Al structure for a reverse bias voltageV= -2V exhibits high values of quantum efficiency (up to 40%) with slight variation in the range of wavelength from 475 nm up to 925 nm, making this structure interesting as a wide band optical sensor device. Finally, the minority carrier (holes) diffusion length of a-SiC:H forTS=120°Cwas calculated and it was found to be≅2.200Å.

Highlights

A-SiC:H is a very promising material in many optoelectronic applications such as solar cell [1], color detector [2], light emitting diode and phototransistor [3]
The experimental results show that the values of quantum efficiency as well as the position of the maximum value owing to the Al=a-SiC:H Schottky junction depend on Ts
These works have shown that the optical band gap, Eg, of the a-SiC:H increases from 2.05 eV up to 2.30 eV with the respective increase of substrate temperature, Ts, from 30 C up to 290 C, and the photosensitivity presents the optimum value at Ts 1⁄4 120 C [8], as well

Summary

THIN FILM

The spectral response of these structures exhibits two maximum values of quantum efficiency. The position of the first maximum owing to the Al=a-SiC:H junction as well as the values of quantum efficiency, for the range of wavelengths from 350 nm up to 700 nm, depends on the substrate temperature, Ts, of the a-SiC:H thin film. In the case that Ts is 120 C, the spectral response of the Al=a-SiC:H=c-Si(n)=Al structure for a reverse bias voltage V 1⁄4 À2 V exhibits high values of quantum efficiency (up to 40%) with slight variation in the range of wavelength from 475 nm up to 925 nm, making this structure interesting as a wide band optical sensor device.

INTRODUCTION

EXPERIMENTAL RESULTS

CONCLUSIONS