Theoretical model of the polarization Coulomb field scattering in strained AlGaN/AlN/GaN heterostructure field-effect transistors

Abstract

The theoretical model of the polarization Coulomb field scattering (PCF) caused by the polarization charge density variation at the AlGaN/AlN interface in strained AlGaN/AlN/GaN heterostructure field-effect transistors has been developed. And the theoretical values for the electron drift mobility, which were calculated using the Matthiessen's rule that includes PCF, piezoelectric scattering, polar optical-phonon scattering, and interface roughness scattering, are in good agreement with our experimental values. Therefore, the theoretical model for PCF has been confirmed.

Effect of Different Gate Lengths on Polarization Coulomb Field Scattering Potential in AlGaN/GaN Heterostructure Field-Effect Transistors

“…3(a). Integration of measured gate capacitance over gate bias yielded the two-dimensional electron gas (2DEG) electron density n 2D under the gate region 26–28,31 , as shown in Fig. 3(b).

Figure 1( a ) Cross-sectional view of the AlGaN/GaN HFETs.

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“…In AlGaN/GaN HFETs, the main scattering mechanisms include polarization Coulomb field (PCF), polar optical phonon (POP), acoustic phonon (AP), interface roughness (IFR), and dislocation (DIS) scatterings 26,31,42–50 . R can be determined by the scattering theories of the 2DEG electrons in AlGaN/GaN HFETs 31,38,46–50 .…”

“…R can be determined by the scattering theories of the 2DEG electrons in AlGaN/GaN HFETs 31,38,46–50 .…”

“…In AlGaN/GaN HFETs, the 2DEG electrons can be written as Ψ( x , y , z ) =  A −1/2 ψ ( z )exp( ik x x  +  ik y y ) 31,38,46,48,50 . Here A is the normalization constant, k x , k y refer to the components of k in the x -direction and y -direction, respectively.…”

“…Polarization Coulomb field (PCF) scattering, stemming from the non-uniform distribution of the strain in the AlGaN barrier layer, can affect the electron mobility, parasitic source access resistance, transconductance, and device linearity in AlGaN/GaN HFETs 26–40 . Based on the perturbation theory, the theoretical model of PCF scattering has been established 31 , which makes it possible to quantitative study of PCF scattering 35–40 . The Hamiltonian of electrons in the source-drain channel can be split into two parts , where is known as the Hamiltonian of the unperturbed system, and is called the perturbation.…”