Absorption and photoconductivity spectra of amorphous multilayer structures.

Oxana Iaseniuc,Mihail Iovu

doi:10.3762/bjnano.11.158

Abstract

The experimental results regarding optical absorption and steady-state photoconductivity of amorphous single-layer structures (Al–As0.40S0.30Se0.30–Al, Al–Ge0.09As0.09Se0.82–Al, and Al–Ge0.30As0.04S0.66–Al) and of an amorphous heterostructure (Al–As0.40S0.30Se0.30/Ge0.09As0.09Se0.82/Ge0.30As0.04S0.66–Al) at different values of the voltage, with positive or negative polarity, applied to the illuminated top Al electrode are presented and discussed. The complex structure of the photocurrent spectra is attributed to the different values of the optical bandgap of the involved amorphous layers (Eg ≈ 2.0 eV for As0.40S0.30Se0.30 and Ge0.09As0.09Se0.82 and Eg ≈ 3.0 eV for Ge0.30As0.04S0.66). The obtained experimental results are discussed taking into account the light absorption depending on the nature and the thickness of each amorphous layer, on the wavelength, and on contact phenomena at the interfaces between different layers and between the amorphous layers and the metal electrodes with different work functions.

Highlights

The As–S–Se, Ge–As–Se, and Ge–As–S ternary glass systems currently attract a lot of attention because of their wide application in IR optics, non-linear optics, photonics, optoelectronics, and as recording media for holography and e-beam lithography [1,2,3]
The thin film layer Ge0.30As0.04S0.66 with the largest bandgap energy, Eg ≈ 3.0 eV [11], which was placed on the top of the multilayer structure, has a thickness of d ≈ 200 nm and was transparent to the incident visible light to reach the other layers with a bandgap energy of Eg ≈ 2.0 eV [12,13] and with a thicknesses of d ≈ 500 nm for Ge0.09As0.09Se0.82 and d ≈ 1000 nm for As0.40S0.30Se0.30
We thank for fruitful discussion and we suggest that for more detailed information regarding the origin of space-chargelimited current (SCLC) in our investigated structures, additional investigations of the I–V characteristics at different temperatures are needed for the estimation of the parameters of localized states

Summary

Introduction

The As–S–Se, Ge–As–Se, and Ge–As–S ternary glass systems currently attract a lot of attention because of their wide application in IR optics, non-linear optics, photonics, optoelectronics, and as recording media for holography and e-beam lithography [1,2,3]. The steady-state photoconductivity spectra of all amorphous thin-film structures were measured with an applied external electric field of E = 5 × 104 V/cm, that is, in the region were the I–V characteristics exhibit linear behavior.

Results

Conclusion