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1

Influence of high Al fraction on reactive ion etching of AlGaN/GaN heterostructures

Gryglewicz J, Stafiniak A, Wosko M, Prazmowska J, Paszkiewicz B

Optica Applicata

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2013

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Vol. 43, nr 1

27--33

EN

In this study, the results of reactive ion etching (RIE) process of diversified Al content AlxGa1–xN/AlN/GaN/sapphire heterostructures were presented. The Al fractions of 22, 25, 31 and 36% were examined. An impact of Al content in the heterostructures on the etch rates and surface morphology was investigated. The influence of used Cl2/BCl3/Ar gas mixture with varying of BCl3 flow on the etch rate of Al0.2Ga0.8N/GaN/sapphire, surface morphology and angle of mesa slope, was discussed.

2

Influence of AlN spacer on the properties of AlGaN/AlN/GaN heterostructures

Wosko M, Paszkiewicz B, Paszkiewicz R, Tlaczala M

Optica Applicata

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2013

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Vol. 43, nr 1

61--66

EN

AlGaN/GaN heterostructures attract attention of many research groups over the last decade because of their superior properties (high mobility and saturation velocity of 2DEG) and strong capability in high frequency/power electronics and sensors applications. One of the factors which reduces the mobility of two-dimensional electron gas (2DEG) is the alloy and interface roughness scattering mechanism occurring at the heterointerface. Mathematical calculations of a wave-function of 2DEG in the channel show that theses two phenomena play an important role, due to the fact that some electrons in 2DEG can migrate into AlGaN barrier and be strongly dissipated. One of the proposed solutions against alloy scattering in the buffer layer is the use of thin AlN spacer at the heterointerface between AlGaN and GaN layers. AlN layer enhances the conduction band offset due to a polarization-induced dipole in the AlN layer, and therefore increases carrier confinement. Several Al0.18GaN0.82/AlN/GaN heterostructures with different AlN spacer layer thickness were grown by MOVPE method for studies of the Hall mobility and sheet carrier concentration of 2DEG. Hall measurements performed using Van der Pauw shown mobility maximum at nominally 1.3 nm AlN spacer thickness and almost linear dependence of sheet carrier concentration with AlN spacer thickness in the range from 0.7 to 2 nm.

3

Solar cells conversion efficiency enhancement techniques

Prażmowska J., Paszkiewicz R., Korbutowicz R., Wosko M., Tłaczala M.

Optica Applicata

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2007

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Vol. 37, nr 1-2

93-99

EN

In order to enhance the conversion efficiency of GaAs p-i-n solar cells GaAs/AlxGa1-xAs QW within intrinsic region or gradation of Al fraction of AlxGa1-xAs emitter and base region were applied. The influence of AlAs Bragg reflectors on the performance of MQWSC was studied theoretically by using SimWindows software.