Effect of the rapid thermal treatment on photodiode preparation of porous silicon prepared by laser assisted etching

مقدم أطروحة جامعية

Husayn, Alaa Abd al-Jabbar

مشرف أطروحة جامعية

Elwan, Elwan Muhammad

الجامعة

الجامعة التكنولوجية

الكلية

-

القسم الأكاديمي

قسم العلوم التطبيقية

دولة الجامعة

العراق

الدرجة العلمية

ماجستير

تاريخ الدرجة العلمية

2011

الملخص الإنجليزي

-In this research; nanostructure porous silicon nPSi was prepared by using laser assisted etching (LAE) of an n-type silicon substrate of resistivity (1.5-4 Ω.cm) in HF of 24%concentration at etching time of 20 minute.

The active nPSi layer was prepared by using three laser wavelengths (Green 532 nm, Red 650 nm and I.R.

810 nm) with a fixed power density of 100 mW/cm2 and variable current density of (10, 20, 30 and 40mA/cm2).

Rapid thermal oxidation and rapid thermal annealing processes were conducted at an oxidation and annealing temperature of 750oC, and different oxidation times (25, 50, 75 and 100sec.) and fixed annealing time (15 sec.).

The morphological characteristics of the nPSi layer through analysing the FESEM images, illustrate that shorter etching wavelength and higher etching current density lead to a decrease of the silicon nanosizes in the nPSi layer.

The rapid thermal treatments will change the nature of the layer from nPSi to partially oxidized nPSilayer.

Porosity layerof nPSi increases with increasing etching current density and it decreases with increasing the etching wavelength .While the thickness of nPSi layer increases with increasing etching wavelength and with increasing etching current density.

Under rapid thermal treatments, the thickness increases too.

The PL measurements show that the increase in energy gap of nPSi layer and the decrease in silicon nanosize in nPSi layer are due to the decrease of the etching wavelength and increase of the etching current density.

The rapid thermal treatments improve the energy gap of the nPSi layer toward the blue shifting.

XRD study illustrates when changing the wavelength from IR to green will change the nature of the silicon surface from single crystallites to polycrystallites with many peaks that disappear after rapid thermal treatments.

The electrical properties of prepared nPSi photodiode; namelycurrent density-voltage characteristics under dark, show that the electric resistivity of the nPSi layer reacha value of 108 Ω.cm, which is higher than the value of the intrinsic silicon.

The photodiode shows a rectifying behaviour with different rectification ratio 3.75 to 13220, and different ideality factors 10.5 to 68.

Rapid thermal treatments improve the photocurrent and dark current of the nPSi photodiode; especially at oxidation time 50 second.

Minimum dark currentof 2 μA/cm2is obtained from nPSi photodiode when prepared with green laser diode at10 mA/cm2 etching current density and 50 second oxidation time.

C-V measurements demonstrate that the behaviour of the resulting junction is more like to Schottky junction.

This study makes it clear that the charge carries depletion process occur in nPSi layer.

Measurements of spectral responsivity of the fabricated nPSi photodiode under preparation ofred laser diode shows a maximum peak value of 3.52 A/W in the visible range at 400nm and this responsivity increases with increasing the etching current density.

Responsivity improves further and reaches 3.54 A/Wunder rapid thermal treatments.

Finally, this work illustrates that the application of laser irradiation in (LAE) process and rapid thermal treatments can giveanPSi photodiode with excellent characteristics.

التخصصات الرئيسية

الفيزياء

الموضوعات

• الخواص الضوئية
• السيليكون
• أشباه الموصلات
• الإلكترونيات

• APA
• MLA
• AMA

لغة النص

الإنجليزية

نوع البيانات

رسائل جامعية

رقم السجل

BIM-305041