The effect of thermal treatment on the photosensitivity of porous silicon prepared by laser assisted etching

Dissertant

Abd al-Zahrah, al-Narjis al-Zamil

University

University of Technology

Faculty

-

Department

Applied Sciences Department

University Country

Iraq

Degree

Master

Degree Date

2008

English Abstract

In this research Porous silicon (Ps) was prepared by using photo electrochemical etching (PEC) of an n-type silicon wafer have festivity (3.5 ft.cm)and thickness (50£ ± 15) pm in hydrofluoric acid(HT)of (23.5 %) concentration at etching time (5 and 15 min) .The irradiation has been achieved by using a laser at a wavelength 810 nm with power 2W and a current density of (20 mA / cm2).The rapid thermal oxidation process occurs at different oxidation times and different oxidation temperatures to enhancement the sensitivity of photo detector device.

The morphological properties of the samples before and after oxidation were carried out by using scanning electron microscopy (SEM)images .We found that increasing in pore diameter and decreasing in column width which separate between pore with increasing etching time .The porosity was increased with increasing etching time it varied from (48 % to 55 %)at etching time 5 and 15 min respectively After rapid thermal oxidation treatment the column size and pore size will be decrease with increasing the oxidation time lead the decrease the porosity.

The porosity for 5 min etching time was varied from (48 to 12 %)after oxidation time 90 sec and 750C, for 15 min etching time the porosity was varied from (55 to 16 %) after oxidation time 90 sec and 750C.

The X-ray diffraction showed the increasing of diffraction intensity with increasing the etching time .After oxidation treatment the diffraction intensity was decreased due to form Si02 structure The energy gap increases with increasing etching time where it varied from (2.0 to 2.3)eV at 5 and 15 min respectively.

After oxidation time 90 sec and 750C the energy gap is increased.

It was varied from (2.08 to 2.19 eV) at 5 min etching time and was varied from (23 tc 2.5 eV) at 15 rain etching time.

The electrical and motto electrical properties show enhancement with thermal treatment .The dark current is decreased from (3608 to 112.5) uA / cm2 at oxidation time 90 sec and 750 CT Photocurrent is increased about seven times rather than fresh sample.

It was varied from (304.2-4966) uA /cm2 at oxidation time 30 sec and 750 C, The optimum value for responsively and performers efficiency occurs at 15 min etching time fabricated through 30 sec and 750 C .A high responsively of 1,35 A / W with high efficiency (gain) reached to 418.5 % can be obtained.

It shows high potential as device applied in photo electronic and optoelectronic integrated.

Main Subjects

Physics

Topics

• Temperatures
• Electrical properties
• Silicon

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-305063