Analysis of Electrothermal Effects in Devices and Arrays in InGaP/GaAs HBT Technology

Abstract

In this paper, the dc electrothermal behavior of InGaP/GaAs HBT test devices and arrays for power amplifier output stages is extensively analyzed through an efficient simulation approach. The approach relies on a full circuit representation of the domains, which accounts for electrothermal effects through the thermal equivalent of the Ohm’s law and can be solved in any commercial circuit simulator. In particular, the power-temperature feedback is described through an equivalent thermal network automatically obtained by (i) generating a realistic 3-D geometry/mesh of the domain in the environment of a numerical tool with the aid of an in-house routine; (ii) feeding the geometry/mesh to FANTASTIC, which extracts the network without performing simulations. Nonlinear thermal effects adversely affecting the behavior of devices/arrays at high temperatures are included through a calibrated Kirchhoff’s transformation. For the test devices, the thermally-induced distortion in I–V curves is explained, and the limits of the safe operating regions are identified for a wide range of bias conditions. A deep insight into the electrothermal behavior of the arrays is then provided, with particular emphasis on the detrimental nonuniform operation. Useful guidelines are offered to designers in terms of layout and choice of the ballasting strategy.

A Critical Review of Techniques for the Experimental Extraction of the Thermal Resistance of Bipolar Transistors from DC Measurements—Part I: Thermometer-Based Approaches

“…The key features of this device are reported in Table 1. Further technological details are provided in [15]. The Si/SiGe NPN HBT was fabricated by Infineon Technologies AG in the framework of the European Project DOTFIVE.…”

“…This offers high flexibility throughout the whole investigation. The collector current I C in forward active mode is expressed as [15,44,45]…”

“…This holds true regardless of the technology and is dictated by the high operating current (and power) densities and the high self-heating thermal resistances. In gallium arsenide (GaAs)-based heterojunction bipolar transistors (HBTs) like InGaP/GaAs and AlGaAs/GaAs, considered the dominant technology for handset power amplifier design, the high thermal resistances are a consequence of (i) the low thermal conductivity of the GaAs substrate (one third of that of silicon), (ii) the lateral heat confinement due to mesa isolation, and (iii) the interlevel dielectric films [9,10,[12][13][14][15]. In silicon/silicongermanium (Si/SiGe) HBTs for mm-wave and near-THz applications, namely, wireless and optical communication, medical equipment, and automotive radars, the increase in thermal resistances is due to technology strategies devised to boost the frequency performance, like (i) adoption of oxide-based shallow/deep trenches and reduction of the spacing between intrinsic transistor and trenches, which hinder the lateral heat propagation from the power dissipation region, and (ii) horizontal scaling of the emitter, which drives higher current (and power) density; such factors have contributed to push the thermal resistances of single-finger HBTs into the thousands of K/W [16][17][18][19][20][21][22].…”

A Multi-Source Co-Simulation Method for the Thermal Stability of GaAs Sub-6G Power Amplifier with Adjustable Bias Current

“…Since the diode and diode-connected HBT have the similar PN junction structure, the TCs of I D and I H can be calculated by the same equation. Under forward bias, the diode current can be written as [32]…”

Compact Modeling of a 3.3 kV SiC MOSFET Power Module for Detailed Circuit-Level Electrothermal Simulations Including Parasitics

“…As an alternative to methods based on numerical tools, we have developed an inhouse approach based on a fully circuital representation of the whole device/circuit for self-consistent static and dynamic ET simulations with SPICE-like programs; considerable efficiency is gained with respect to [12][13][14] since the thermal problem is modeled with an equivalent thermal network derived through an advanced model-order reduction algorithm. The approach has been successfully used for devices/circuits in large variety of technologies, like an IGBT-based boost converter [18], a multicellular SiC power MOSFET operating under harsh conditions [19], and InGaP/GaAs HBT arrays for power amplifiers [20].…”