Application of superlattice gate and modulation-doped buffer for GaAs power MESFET grown by MBE

A new power GaAs MESFET (SGMBT), using the undoped superlattice gate and modulation-doped (MD) buffer, has been fabricated successfully by MBE. A much higher gate-drain breakdown voltage (30 V) and lower gate reverse leakage current have been obtained due to the existence of the undoped AlGaAs/GaAs superlattice gate insulator. The use of MD buffer structure introduces a high output resistance and low trap concentration at AlGaAs/GaAs interface. The degradation region at channel-buffer interface is estimated to be smaller than 40 Å. Thus the sharpness and smoothness between active channel and buffer is truly improved by the insertion of MD structure. The maximum output saturation current and output power of SGMBT are 300 mA/mm and 0.67 W/mm, respectively. By optimizing the device geometry and gate dimension, the output performance of SGMBT can be improved further.     

Microwave complementary doped-channel field-effect transistors

In this paper, the device performance and complementary inverter of the InGaP/InGaAs/GaAs doped-channel field-effect transistors (DCFETs) by two-dimensional semiconductor simulation are demonstrated. Due to the relatively large conduction (valance) band discontinuity at InGaP/InGaAs interface, it provides good confinement effect for transporting carriers in InGaAs channel layer for the n-channel (p-channel) device. The large gate turn-on voltage is achieved due to the employment of the wide energy-gap InGaP material as gate layer. The _ft$f_t$ and _fmax$f_{max}$ are of 6.5 (2.1) and 25 (5) GHz for the n-channel (p-channel) device. Furthermore, the co-integrated structures, by the combination of n- and p-channel field-effect transistors, could form a complementary inverter and the relatively large noise margins are achieved.     

On a nonlinear wave equation with boundary damping

This paper is concerned with the existence and decay of solutions of the mixed problem for the nonlinear wave equation with boundary conditions Here, Ω is an open bounded set of with boundary Γ of class C²; Γ is constituted of two disjoint closed parts Γ₀ and Γ₁ both with positive measure; the functions μ(t), f(s), g(s) satisfy the conditions μ(t) ≥ μ₀ > 0, f(s) ≥ 0, g(s) ≥ 0 for t ≥ 0, s ≥ 0 and h(x,s) is a real function where x ∈ Γ₁, ν(x) is the unit outward normal vector at x ∈ Γ₁ and α, β are non‐negative real constants. Assuming that h(x,s) is strongly monotone in s for each x ∈ Γ₁, it is proved the global existence of solutions for the previous mixed problem. For that, it is used in the Galerkin method with a special basis, the compactness approach, the Strauss approximation for real functions and the trace theorem for nonsmooth functions. The exponential decay of the energy is derived by two methods: by using a Lyapunov functional and by Nakao's method. Copyright © 2013 John Wiley & Sons, Ltd.