Yüksek performanslı AlxGa1-xN metal-yarıiletken-metal fotodiyotların büyütülmesi, üretilmesi ve karakterizasyonu

AbstractTHE GROWTH, FABRICATION, AND CHARACTERIZATION OFHIGH PERFORMANCE AlxGa1-xN METAL-SEMICONDUCTOR-METAL PHOTODIODESSerkan BütünM.S. in PhysicsSupervisor: Prof. Dr. Ekmel ÖzbaySeptember 2006High performance UV photodetectors have attracted unwarrantedattention for various applications, such as in military, telecommunication, andbiological imaging, as an AlxGa1-xN material system is also rather suitable forsuch applications. Its direct band gap covers the spectrum from 200 nm to 360nm by way of changing the Al concentration in the compound. In this presentthesis, the design and growth of an Al0.75Ga0.25N template on sapphire substrateand a deep-UV photodiode with a cut off wavelength of 229 nm that wasfabricated on the Al0.75Ga0.25N template is presented. A responsivity of 0.53A/W was attained corresponding to a detectivity of 1.64 × 1012 cmHz1/2/W at a50 V bias and 222 nm UV light illumination. The UV/VIS rejection ratio ofseven orders of magnitude was achieved from the fabricated devices. Thesecond work that was conducted in this thesis was the growth of a semi-insulating (SI-) GaN template. We also fabricated visible-blind photodetectorson this semi-insulating (SI-) GaN template. Furthermore, we fabricated identicalsamples on a regular GaN template in order to investigate any possibleiimprovement. The improvement found was obvious in terms of dark current. Adark current density of 1.96 × 10-10 A/cm2 at a 50 V bias voltage for an SI-GaNphotodetector was obtained, which is four orders of magnitude lower thandevices on a regular GaN template. Devices on an SI-GaN had very highdetectivity, and therefore, SI-GaN was used for low level power detection. Thephotogenerated current was well above the dark current that was under theillumination of just a few picowatts of UV light.Keywords: Photodetector, Photodiode, GaN, AlGaN, Metal-semiconductor-metal, Semi-insulatingii