Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı
An InvestIgatIon of electronIc transport processes In low dImensIonal semIconductor systems
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| An InvestIgatIon of electronIc transport processes In low dImensIonal semIconductor systems
In this work electronic transport processes have been investigated theoretically and experimentally on GaAs/AlxGa1-xAs quantum well infrared photodetector (QWIP) structures which are examples of low dimensional semiconductor systems. The structures, which are named as staircase type QWIP are based on GaAs/AlxGa1-xAs and have n-type doped quantum wells with stepped barriers including various Al concentrations. In these structures electronic transport processes have been studied at low and high electric and magnetic fields theoretically and experimentally. 3 different QWIP structures have been used in the studies. Among these, 2 structures have been prepared being suitable for both vertical and parallel transport. In this way, properties of the same structure have been studied comparatively by the applied vertical and parallel electrical fields. In these studies, I-V characterization under low and high electrical fields, Hall effect characterization and magnetoresistance measurements at the temperature range of 4-300 K have been done. Fourier transform infrared spectroscopy (FTIR) mesurements have been done at room temperature intended for optical characterization. At first, the structures have been modelled theoretically, energy band diagrams were prepared. Experimentally obtained data have been compared with these theoretical results. In the quantum wells of the structures a bound state and just above the barriers quazi-bound states have been calculated. For vertical samples, activation energies corresponding to 8-10 µm wavelength have been determined. It has been determined that at low temperatures tunneling, at high temperatures thermally assisted tunneling and thermionic emission are the effective transport mechanisms for vertical samples. As the result of theoretical calculations and Hall measurements parallel conduction has been concluded for parallel samples. At low temperatures and low magnetic fields negative magnetoresistance effect has been observed. It has been determined that between 18-25 μm wavelength range, multiphonon absorption is dominant due to GaAs.
Fatma AYDOĞMUŞ Tez Adı : Spinör Tipi İnstanton Çekicilerinin Faz Uzayında Davranışları Danışman : Prof. Dr. K. Gediz AKDENİZ Anabilim Dalı : Fizik Programı : Yüksek Enerji ve Plazma Fiziği Mezuniyet Yılı : 10.01.2013 Tez Savunma Jürisi : Prof. Dr. K. Gediz AKDENİZ Prof. Dr. Haşim MUTUŞ Prof. Dr. Hasan TATLIPINAR Prof. Dr. Sehban KARTAL Prof. Dr. Handan GÜRBÜZ Yüklə 0,84 Mb. Dostları ilə paylaş:
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