MOCVD ile Büyütülen Al0.3Ga0.7N/GaN HEMT'nin Yapısal, Optik ve Elektriksel Özelliklerinin Araştırılması

Bu çalışmada c-eksenli safir alttaş üzerine MOCVD yöntemiyle büyütülen Al0.3Ga0.7N/GaN yüksek elektron hareketli transistör (HEMT) yapısı incelenmiştir. Bu yapının optik, morfolojik ve elektriksel özellikleri X-Işını Kırınımı (XRD), Fotoluminesans (PL), Ultraviyole ve görünür ışık (UV-Vis), Atomik Kuvvet Mikroskobu (AFM) ve Hall-Direnç ölçümleri ile belirlendi. Simetrik ve asimetrik düzlemlerde XRD metodu ile 2θ, Yarım Maximum'daki Tam Genişlik (FWHM), örgü parametreleri, kristal boyutu, zorlama, gerilme ve dislokasyon değerleri hesaplanmıştır. GaN'nin doğrudan bant aralığı PL ölçümleriyle 3.24 eV olarak belirlenir. AlGaN katmanının iletiminin UV-Vis'de 360 nm'de başladığı görülmektedir. Hall-Direnç ölçümlerinde, HEMT yapısının taşıyıcı yoğunluğunun sıcaklıktan etkilenmediği ve hareketlilik değerinin yüksek olduğu ölçüldü. Taşıyıcı yoğunluğu ve hareketlilik değerleri oda sıcaklığında sırasıyla 5.82x1015 1/cm3 ve 1198 cm2 /V olarak belirlendi. En düşük sıcaklık değerinde (25 K) sırasıyla 5.19x1015 1/cm3 ve 6579 cm2 /V olarak hesaplandı.

Investigation of structural, optical and electrical properties of Al0.3Ga0.7N/GaN HEMT grown by MOCVD

In this study, Al0.3Ga0.7N/GaN high electron mobility transistor (HEMT) structure is investigated grown over c- oriented sapphiresubstrate by using Metal Organic Chemical Vapor Deposition (MOCVD) method. Structural, optical, morphological and electricalcharacteristics of this structure are determined by X-ray diffraction (XRD), Photoluminescence (PL), Ultraviolet (UV-Vis.), AtomicForce Microscopy (AFM) and Hall- Resistivity measurements. By using XRD method, 2θ, Full Width at Half Maximun (FWHM),lattice parameters, crystallite size, strain, stress and dislocation values are calculated on symmetric and asymmetric planes. Directband gap of GaN is determined by PL measurements as 3.24 eV. It is seen that conduction of AlGaN layer starts at 360 nm in UVVis. In Hall-Resistivity measurements, it is noticed that carrier density of HEMT structure is not effected by temperature andmobility value is high. Carrier density and mobility values are determined as 5.82x1015 1/cm3and 1198 cm2/V.s at roomtemperature, respectively. At the lowest temperature point (25 K) they are calculated as 5.19x1015 1/cm3 and 6579 cm2/Vs,respectively.

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