Li Zhi-Wei

Memristance controlling approach based on modification of linear M—q curve

The memristor has broad application prospects in many fields, while in many cases, those fields require accurate impedance control. The nonlinear model is of great importance for realizing memristance control accurately, but the implementing complexity caused by iteration has limited the actual application of this model. Considering the approximate linear characteristics at the middle region of the memristance-charge (M—q) curve of the nonlinear model, this paper proposes a memristance controlling approach, which is achieved by linearizing the middle region of the M—q curve of the nonlinear memristor, and establishes the linear relationship between memristances M and input excitations so that it can realize impedance control precisely by only adjusting input signals briefly. First, it analyzes the feasibility for linearizing the middle part of the M—q curve of the memristor with a nonlinear model from the qualitative perspective. Then, the linearization equations of the middle region of the M—q curve is constructed by using the shift method, and under a sinusoidal excitation case, the analytical relation between the memristance M and the charge time t is derived through the Taylor series expansions. At last, the performance of the proposed approach is demonstrated, including the linearizing capability for the middle part of the M—q curve of the nonlinear model memristor, the controlling ability for memristance M, and the influence of input excitation on linearization errors.

Computation of the locus crossing point location of MC circuit

In this paper, the crossing point property of the i–v hysteresis curve in a memristor–capacitor (MC) circuit is analyzed. First, the ideal passive memristor on the crossing point property of i–v hysteresis curve is studied. Based on the analysis, the analytical derivation with respect to the crossing point location of MC circuit is given. Then the example of MC with linear memristance-versus-charge state map is demonstrated to discuss the drift property of cross-point location, caused by the frequency and capacitance value.

Electron mobility limited by surface and interface roughness scattering in AlxGa1−xN/GaN quantum wells

The electron mobility limited by the interface and surface roughness scatterings of the two-dimensional electron gas in AlxGa1−xN/GaN quantum wells is studied. The newly proposed surface roughness scattering in the AlGaN/GaN quantum wells becomes effective when an electric field exists in the AlxGa1−xN barrier. For the AlGaN/GaN potential well, the ground subband energy is governed by the spontaneous and the piezoelectric polarization fields which are determined by the barrier and the well thicknesses. The thickness fluctuation of the AlGaN barrier and the GaN well due to the roughnesses cause the local fluctuation of the ground subband energy, which will reduce the 2DEG mobility.

Growth and Characterization of an a-Plane InxGa1-xN on a r-Plane Sapphire

The non-polar a-plane (110) InxGa1−xN alloys with different indium compositions (0.074 ≤ x ≤ 0.555) were grown on r-plane (102) sapphire substrates by metalorganic chemical vapor deposition, and the indium compositions x are estimated from x-ray diffraction measurements. The in-plane orientation of the InxGa1−xN with respect to the r-plane substrate is confirmed to be [100]sapphire|| [110]InxGa1−xN and [101]sapphire|| [0001]InxGa1−xN. The effects of substrate temperature, reactor pressure and trimethylindium input flow on the indium incorporation and growth rate are investigated. The morphology of the a-plane InxGa1−xN is found to be significantly improved with the decreasing indium composition x and growth rate. Moreover, the in-plane anisotropic structural characteristics are revealed by high resolution x-ray diffraction employing azimuthal dependence, and the degree of anisotropy decreases with the increase of indium composition.