The Influence of AlGaN/GaN Heteroepitaxial Structure Fractal Geometry on Size Effects in Microwave Characteristics of AlGaN/GaN HEMTs

Abstract

The investigation of size effects appearing in the dependence of AlGaN/GaN HEMT high-frequency characteristics on channel width d and number of sections n is conducted using the notions of measure, metric and normed functional (linear) spaces. In accordance with the results obtained, in local approximation the phenomenon of similarity can exist, not only in metric spaces of heteroepitaxial structures, but also in the defined on them functional spaces of the measures of these structures’ additive electrophysical characteristics. This provides means to associate size effects of the HEMTs with their structure material fractal geometry. The approach proposed in the work gives an opportunity, not only to predict the size of the structural elements (e.g., channel width and number of sections) of the transistor with the desired characteristics, but also to reconstruct its compact model parameters, which significantly speeds up the development and optimization of the HEMTs with the desired device characteristics. At transferring to the global approximation, when the topological and fractal dimensions of the structure coincide, its electrophysical characteristics, and subsequently, the values of the compact model equivalent circuit parameters, as well as HEMT high frequency characteristics, follow the classic (linear) laws peculiar to the spaces of integer topological dimensions DT.

Physical nature of size effects in TiAlNiAu/GaN ohmic contacts to AlGaN/GaN heteroepitaxial structures

“…The observed size effects are due to the structural elements forming the OC having lateral inhomogeneities in their internal structure. As reported in [22,[30][31][32][33], it can be successfully described using the apparatus of fractal geometry.…”

“…Recently, it has been shown that the functional electrophysical properties of semiconductor materials (in particular, the resistive resistance of epitaxial GaN/AlGaN layers [22]) in the local approximation also exhibit scaling and statistical selfsimilarity properties. This made it possible to describe the size effects in the functional dependencies (conductivity) of semiconductor layers using the fractal geometry mathematical tool [22,23]. These facts suggest that the specific electrophysical characteristics of OCs to n-GaN should also obey similar laws.…”

“…The reason for this is the dependence of the relative electrophysical characteristics of OC on their various linear dimensions L and W [22,30]. The observed size effects are due to the structural elements forming the OC having lateral inhomogeneities in their internal structure.…”

Влияние Морфологии Поверхности Микрополосковой Линии СВЧ На Ее Передаточные Характеристики

“…Калибровка измерительных трактов портов осуществлялась по S-параметрам согласованием на проход ( " Thru"), на нагрузку 50 Ом (Load), на холостой ход ( " Open") и на короткое замыкание ( " Short"). После этого проводилась процедура дэ-эмбеддинга (de-embedding) и экстракция параметров эквивалентных элементов ЭС секции КЛП [13,14].…”

Conversion of the anomalous skin effect to the normal one in thin-film metallic microwave systems

“…Obviously, the variety of influence ways of various geometric forms of Brownian surfaces relief and their grain substructures on metal films functional characteristics is not fully realized yet. Specifically, it is proven by the existence of a number of nontrivial electrophysical properties based on lateral inhomogeneities extended to hundreds micron [31][32][33].…”