Bias induced strain in AlGaN∕GaN heterojunction field effect transistors and its implications

Abstract

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An analytical charge control model for AlGaN/GaN HEMT including the gate bias dependence on polarization charge

“…So 2DEG channel charge in these regions decreases, resulting in increase of source and drain resistances. This could explain a portion of current collapse [6]. Our model when extended can quantify these effects.…”

“…Poisson's equation is solved using the modified piezoelectric charge [5], [6] to obtain an analytical expression for 2DEG channel charge. In section III comparisons of this model with the models reported earlier which are without electromechanical coupling, are done.…”

Influence of the channel electric field distribution on the polarization Coulomb field scattering in AlGaN/AlN/GaN heterostructure field-effect transistors

“…where e 31 and e 33 are the piezoelectric coefficients, C 13 and C 33 are the elastic constants, E Z is the transverse electric field and ε x = (a Ga N − a AlGa N )/a AlGa N is the in-plane strain (where, a AlGa N and a Ga N are corresponding to the equilibrium lattice parameters of AlGaN and GaN, respectively), the values of these parameters are shown in Table I. 14 Here, it is assumed that the thin AlN interlayer is tensile strained to the lattice constant of a GaN .…”

Enhanced effect of strain-induced polarization Coulomb field scattering in AlN/GaN heterostructure field-effect transistors

“…6 As a result, for the range of 0 $ À0.4 V, the LO phonon scattering and interface roughness scattering are comparable to the PCF scattering which results in an unchanged mobility for the 2DEG electrons at different gate biases. Due to the converse piezoelectric effect, the gate biases will exacerbate the strain variation of the AlN barrier layer under the Schottky contacts, 18 and increase the difference between q Mat and q G . Since the elastic scattering potential of the polarization Coulomb field is proportional to the nonuniform polarization between q Mat and q G , q S/D , increasing the reverse gate bias results in a stronger polarization Coulomb field scattering in the 2DEG electrons.…”