Sains Malaysiana 40(1)(2011): 5–8

Characterization of Ge Nanostructures Embedded Inside Porous Silicon for Photonics Application

(Pencirian Nanostruktur Ge Terbenam di dalam Silikon Berliang untuk Aplikasi Fotonik)

A.F. Abd Rahim ^1,2 *, M.R. Hashim¹ & N.K. Ali³

¹School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia

²Faculty of Electrical Engineering, Universiti Teknologi MARA, 13500 Permatang Pauh, Penang Malaysia

³Faculty of Electrical Engineering

Department of Electronic Engineering, Universiti Teknologi Malaysia

81310 Skudai, Johor, Malaysia

Received: 7 December 2009 / Accepted: 13 July 2010

ABSTRACT

In this work we prepared germanium nanostructures by means of filling the material inside porous silicon (PS) using conventional and cost effective technique, thermal evaporator. The PS acts as patterned substrate. It was prepared by anodization of silicon wafer in ethanoic hydrofluoric acid (HF). A Ge layer was then deposited onto the PS by thermal evaporation. This was followed by deposition of Si layer by thermal evaporation and anneal at 650οC for 30 min. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400οC for 10 min to form metal semiconductor metal (MSM) photodetector. Structural analysis of the samples was performed using energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). EDX spectrum suggests the presence of Ge inside the pores structure. Raman spectrum showed that good crystalline structure of Ge can be produced inside silicon pores with a phase with the diamond structure by (111), (220) and (400) reflections. Finally current-voltage (I-V) measurement of the MSM photodetector was carried out and showed lower dark currents compared to that of Si control device. Interestingly the device showed enhanced current gain compared to Si device which can be associated with the presence of Ge nanostructures in the porous silicon

Keywords: Ge; porous; Raman spectroscopy; silicon thermal evaporation

ABSTRAK

Di dalam kajian ini nano struktur Ge disediakan dengan mengisi Ge ke dalam liang Si menggunakan kaedah konvensional dan kos efektif iaitu penyejatan haba. Si berliang bertindak sebagai substrat yang beracuan. Si berliang disediakan melalui proses anodisasi wafer Si di dalam larutan asid HF bersama etanol. Lapisan Ge diendapkan di atas liang Si ini menggunakan teknik penyejatan haba. Kemudian proses diteruskan dengan endapan lapisan Si menggunakan teknik yang sama dan dipanaskan pada suhu 650οC selama 30 min. Proses ini disempurnakan dengan mengendap logam Ni sebagai sesentuh menggunakan teknik penyejatan haba dan diikuti dengan pemanasan logam sentuh pada suhu 400οC selama 10 min bagi membina pengesan cahaya logam-separuh pengalir-logam. Analisis struktur bahan kajian dilaksanakan menggunakan teknik EDX, SEM, XRD dan spektroskopi Raman. Spektrum EDX mencadangkan kehadiran Ge di dalam struktur liang Si. Spektrum Raman menunjukkan struktur hablur yang baik bagi Ge dapat dihasilkan di dalam liang Si dengan kehadiran fasa berbentuk intan dengan pantulan pada satah (111), (200) dan (400). Akhirnya pengukuran arus voltan untuk pengesan cahaya yang dibina menunjukkan arus gelap yang rendah berbanding arus gelap peranti kawalan Si. Menariknya, peranti pengesan cahaya ini menunjukkan peningkatan gandaan arus berbanding peranti Si dan ini boleh dikaitkan dengan kehadiran struktur nano Ge di dalam liang Si.

Kata kunci: Ge; penyejatan haba; Si berliang; spektroskopi raman

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*Corresponding author; email: alhan570@ppinang.uitm.edu.my