Development of global calibration for accurate GaAs-PHEMT simulation

Abstract

Today's GaAs PHEMTs make it possible to cover applications of an extremely wide frequency range, as high as 100 GHz, with a single device type. In this paper, a set of models and calibrations for the predictive device simulation of GaAs PHEMTs is developed. The simulation setup includes a description of the device geometry. In particular, a realistic representation of the region between the ohmic contacts and the channel is included along with the fitting procedure of the simulation parameters and the necessary transport and interface models. In addition, special emphasis has been placed on a simultaneous fitting of currents and capacitances. The resulting setup allows to describe different devices without changing any nontechnology dependent parameters and thus provides a global calibration within a given device family. This capability is demonstrated by comparing the measured and simulated results of five very different devices which cover gate lengths from 120 to 500 nm, transconductances from 400 to 800 mS/mm, and ungated channel lengths from 70 to 600 nm Index Terms-Calibration, GaAs, millimeter wave devices, MODFET, semiconductor heterojunctions, simulation. I. INTRODUCTIONT HE GaAs wafer industry has experienced phenomenal growth over the last few years [1]. Today, MESFETs are the working horse for most large volume applications. As the demands on device performance are increased other transistors like pseudomorphic HEMTs (PHEMTs) and HBTs are becoming very important.PHEMTs on GaAs are able to cover an extremely wide frequency range with very good competitiveness over other technologies. Depending on the application, different requirements arise. The lower important frequency range 0.9/1.9 GHz is used for mobile communication where HEMTs are competing with various other technologies such as LDMOS, Si/Ge-HBTs, III-V-HBTs, and GaAs-MESFETs. Therefore, cheap volume production is one of the most important requirements. These HEMTs will typically have gate lengths between 500 nm and 1 m and breakdown voltages over 10 V. Frequency bands around 40 GHz for base stations lead to a trade off between RF performance and power capability. HEMTs for applications around 77 GHz and 94 GHz are usually optimized in first place with respect to their RF performance. Therefore, they typically exhibit gate lengths below 150 nm and breakdown voltages around 5 V.

Broadband Distortion Cancellation Technique in GaAs HJFET and GaN FET Cascode Amplifier

“…Thus, the behavior of gain characteristics can be adjusted by the gm-profile design. In addition, the various gm-profiles can be designed by the doping concentration and the thickness of epitaxial layers of HJFET [11]. In this time, we aimed at the gm-profile like type-a to obtain the gain expansion.…”

Performance limits of simulation models for noise characterization of mm-wave devices

“…Equation (1) is descretized in time, and equations (1)(2)(3)(4)(5) are discretized in space in one, two or three dimensions. The descretized system of equations (obtained by using Finite-Difference or Finite Element method) is numerically solved to get the required characteristics.…”

“…The drift-diffusion model [1][2][3], hydrodynamic models [4][5][6], and Monte-Carlo code [7][8][9][10] are considered as the most popular and efficient physical noise simulators. They are able to determine the current-voltage characteristics, the smallsignal parameters, and the terminal current and voltage fluctuations which results from the internally generated noise inside the device.…”

Static simulation of pseudomorphic heterostructure FETs at medium/high temperatures

“…A more realistic HFET simulator must consider the electron transport across the heterojunction, between the channel and the upper barrier layer, where quantum effects are involved. Therefore, the Schrödinger and Poisson equations should be solved self-consistently [3], or at least a thermionic carrier transport mechanism at the heterojunction needs to be included [4,5]. But in both cases, there has been no emphasis on the temperature performance of the device.…”

“…This mechanism must be included in order to obtain reliable results when the influence of temperature variations is analysed [10]. The effective length of the thermionic field emission model, l ef , has already been used as a fitting parameter for the static simulations of P-HFETs at 300 K [4,5]. In this paper we examine the long P-HFET behaviour operating at the medium/high temperature range.…”