Effect of Thermal Treatments on the Schottky Contact between Polycrystalline PbS Thin Film and Gold

Abu Bakar,Shaheed Khan,Muhammad Mansoor,Muneeb Asim

doi:10.4028/www.scientific.net/kem.778.230

Abu Bakar, Shaheed Khan + Show 2 more

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https://doi.org/10.4028/www.scientific.net/kem.778.230

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Abstract

Electrical characteristics of semiconductor to metal (S-M) contacts i.e. Schottky contacts, play a vital role towards the performance of the device. The formation of a Schottky contact requires precise thermal treatment, which also affects the electrical characteristic of the junction. In present study, a thin layer of polycrystalline lead sulfide (PbS) was deposited on quartz substrate using chemical bath technique. Metallic electrodes of aluminum and gold were deposited on the each side of the semiconductor film by thermal evaporation method. The aluminum and gold films were 10 nm and 200 nm thick, respectively. Latter, the substrates were thermally treated in air for various durations and the effect of the thermal treatments was evaluated by I-V measurements. It was found that anomalies in the electrical behavior of the S-M contacts were mitigated with the treatments. A change from 0.1 x 10-6A to 0.4 x 10-6A in saturation current was observed. Similarly, the ideality factor (at Vth<<Vd) of the S-M contact was 12 on pristine PbS, while it reduced to 2.7 after the thermal treatment, which indicates an improved Schottky contact.

Highlights

Lead sulfide (PbS) is a IV-VI semiconductor with cubic structure having a direct narrow band gap of 0.41 eV at 300 K, which finds their extensive application in detectors
An electrical contact is the interface between the current carrying members of electronic devices that assure the continuity of electric circuit
An ohmic contact is a low-resistance junction providing current conduction in both directions, contrarily a Schottky contact generates a conduction barrier between semiconductor and metal junction, which is analogous to a p-n junction [1]

Summary

Introduction

Lead sulfide (PbS) is a IV-VI semiconductor with cubic structure having a direct narrow band gap of 0.41 eV at 300 K, which finds their extensive application in detectors. Gold was selected with thin buffer layer of aluminum as contact materials for PbS semiconductor thin film. The contacts were thermally treated at various temperatures and characterized by using scanning electron microscope (SEM), X-ray diffraction and current-voltage (I-V) testing.

Results

Conclusion