Progress in GaN devices performances and reliability

Abstract

With the DARPA Wide Bandgap Semiconductor Technology RF Thrust Contract, TriQuint Semiconductor and its partners, BAE Systems, Lockheed Martin, IQE-RF, II-VI, Nitronex, M.I.T., and R.P.I. are achieving great progress towards the overall goal of making Gallium Nitride a revolutionary RF technology ready to be inserted in defense and commercial applications. Performance and reliability are two critical components of success (along with cost and manufacturability). In this paper we will discuss these two aspects. Our emphasis is now operation at 40 V bias voltage (we had been working at 28 V). 1250 µm devices have power densities in the 6 to 9 W/mm with associated efficiencies in the low-to mid 60 % and associated gain in the 12 to 12.5 dB at 10 GHz. We are using a dual field-plate structure to optimize these performances. Very good performances have also been achieved at 18 GHz with 400 µm devices. Excellent progress has been made in reliability. Our preliminary DC and RF reliability tests at 40 V indicate a MTTF of 1E6hrs with1.3 eV activation energy at 150 0 C channel temperature. Jesus Del Alamo at MIT has greatly refined our initial findings leading to a strain related theory of degradation that is driven by electric fields. Degradation can occur on the drain edge of the gate due to excessive strain given by inverse piezoelectric effect.

Effects of a GaN cap layer on the reliability of AlGaN/GaN Schottky diodes

“…Wide‐bandgap semiconductors, such as GaN, SiC, and diamond, have attracted a lot of interest for applications in high‐power and high‐temperature applications due to their wide‐bandgap properties . Among these materials, GaN is a very promising one not only because of its large critical breakdown field strength and high saturation velocity, but also because of the high sheet carrier density and electron mobility of the two‐dimensional electron gas (2DEG) in the channel layer of the AlGaN/GaN heterojunctions . AlGaN/GaN‐based Schottky barrier diodes (SBDs) and heterostructure field‐effect transistors (HFETs) have gone through rapid development and been proved to be excellent candidates for applications in the area of high‐power switching.…”

Electric-field and Thermally-activated Failure Mechanisms of AlGaN/GaN High Electron Mobility Transistors

“…The degradation takes place at the gate-drain edge (or at both edges if V DS =0 V and the gate is negatively biased) [3]. On the other hand, during long duration (>1000 hours) DC or rf operating life tests at high temperatures, a thermally-activated degradation of drain current has been observed, with a very wide range of activation energies, from 1.05 eV [4] to 2.47 eV [5] [6]. The physical mechanism leading to the latter thermally-activated longterm degradation of GaN HEMT electrical characteristics is unknown, especially considering that Schottky and ohmic contacts are generally stable even at very high temperatures.…”