Analytic Estimation of Two-Dimensional Electron Gas Density and Current-Voltage Characteristic in AlGaN/GaN HEMT’s

Abstract

This paper is mainly dedicated to understand the phenomena governing the formation of two-dimensional electron gas (2DEG) confined in the quantum well which hold the role of the channel in the high electron density transistors (HEMT) based on AlGaN / GaN heterojunction. The theory takes into account: the crystal structure, the spontaneous and piezoelectric polarization concept, the formation mechanism of two-dimensional electron gas at the AlGaN / GaN interface, the approximate resolution of the Poisson and Schrödinger equations to determine the density of Two-dimensional electron gas after the analytical formula of the current-voltage characteristic is established. Our study is also concerned with the dependence of the twodimensional electron gas density on the following technological parameters: Aluminum molare fraction, AlGaN layer thickness and AlGaN layer doping, In order to control the influence of these parameters on the device performance. Finally, the current-voltage characteristic which reflects the variation of the drain-source current as a function of the modulation of the gate voltage has been discussed. Keyword: 2DEG INTRODUCTIONThe area of microelectronics has been marked by an increase in the demand for components which can operate in frequency increasingly higher [1][2][3]. Emerging needs in this area are not only related to the telecommunications market, but in other areas of application such as embedded electronics at bound for the automotive and aeronautic. The largest concerns in semiconductor integrated circuits are high-speed operation and low power consumption [4]. Since the 90s, a new generation of semiconductor components (HEMT) is under study and evaluation thanks to the advent of wide band gap materials such as GaN [5], GaN based devices are very useful for high frequency high temperature microwave applications such as radar systems [6]. Transistors AlGaN / GaN HEMTs results are very promising for power electronics and high frequency due to their two-dimensional electron gas 2DEG high density and high mobility as well as to their high breakdown field [7].To develop a reliable model of HEMT, an accurate estimate of the two-dimensional electron gas density at AlGaN / GaN interface is of considerable importance. A number of charge control models for HEMTs have been developed to characterize the 2-DEG concentration. These models are useful as they provide an insight into the physical operation of the device, but they generally require simplifying assumptions for the 2DEG density. Some models assume a linear dependency of 2DEG density at the gate bias, but the values of 2DEG density are underestimated near the threshold [8], [9]. Other models offer a

New investigation of an E-mode metal-insulator-semiconductor AlInN/AlN/GaN HEMT with an Au-T-gate

“…The primary parameter to enhance the performance of AlInN/AlN/GaN HEMTs is the concentration of 2DEG (ns) [21]. Understanding the physical phenomena governing the operation of the HEMT and the formation of a 2DEG requires solving the Schrödinger's and Poisson's equation [23]. The solution of Schrodinger's equation gives a quantized description of the density of states in the presence of quantum mechanical confining potential variations.…”

DC and RF characteristics of 20 nm gate length InAlAs/InGaAs/InP HEMTs for high frequency application

“…Introduction of schottky layer also enhances the device performance by increasing 2-DEG electron density, improving threshold voltage control [26,27]. The phenomena dominate the formation of two-dimensional electron gas (2DEG) confined in the quantum well which take the role of the channel in the high electron density transistors (HEMT) based on AlGaN / GaN and InAlAs/InGaAs/InP heterojunction [28]. In this paper, we report the main characteristics of 20nm gate-length InAlAs/InGaAs on InP substrate HEMT.…”